Steak Sandwich with Caramelized Onion, Mozzarella & Spicy Sauce

Keto | Paleo Option | Gluten-Free | Low-carb | High-Protein

Sink your teeth into this irresistible One Pan Fillet Steak Sandwich with Caramelized Onion, Capsicum, Mozzarella Cheese, and a kick of Spicy Sauce.

It’s a celebration of bold Flavors and rich textures, all perfectly coming together to create a symphony in your mouth. Juicy fillet steak, cooked to perfection, is tender and rich. Paired with sweet, tangy caramelized onion and capsicum, and melted mozzarella cheese, which adds creamy indulgence in every bite. Fresh tomato slices and peppery rocket bring a refreshing balance to the richness of the steak and cheese, while the spicy sauce adds the perfect kick to finish it off.

All of these delicious ingredients are nestled between slices of low-carb olive sourdough bread, which adds a hearty crunch. Of course, you can use your Favorite bread or even enjoy it without any bread, the combination of steak, caramelized onion, capsicum, mozzarella, and spicy sauce is just as flavourful on its own. It’s a perfect full meal! Simply add arugula (rocket) to your plate, top it with the steak, and cover it with the spicy sauce and melted mozzarella. Add caramelized onion, capsicum, and tomato slices on the side, and enjoy this high-protein, scrumptious dish in all its glory. check out How to Adapt This Fillet Steak Sandwich to Your Diet.

Ingredients Needed to Make This Steak Sandwich with Caramelized Onion, Mozzarella & Spicy Sauce

• Fillet Steaks: The star of the sandwich, providing a rich, meaty flavour and high-quality protein.
• Avocado Oil or Olive Oil: Used for cooking the steak and vegetables, adding a subtle flavour and healthy fats.
• Butter: Enhances the flavour of the steak and gives it a beautiful sear.
• Garlic Clove & Rosemary Sprigs: Adds aromatic flavours to the steak.
• Salt & Pepper: Basic seasonings to enhance the natural flavours of the ingredients.
• Red Capsicum, Onions, Red Chilli: Adds sweetness, tanginess, and a bit of heat to the sandwich.
• Oregano & Smoked Paprika: Spices that add depth of flavour to the caramelised vegetables.
• Balsamic Vinegar & Brown Sweetener or Honey: Creates a sweet and tangy glaze for the caramelised vegetables.
• Low-Carb Olive Sourdough Bread: Adds a nice crunch and texture as the base of the sandwich.
• Mozzarella Cheese: Adds a creamy, melty element to the sandwich.
• Tomato & Fresh Rocket: Provides a fresh, crisp contrast to the rich flavours of the steak and cheese.

Sauce Ingredients:

• Red Chilli, Olive Oil Mayonnaise, Tomato Sauce, Dijon Mustard, Oregano, Smoked Paprika, Black Pepper, Olive Oil: Combines to create a hot, tangy, and utterly delicious sauce that ties all the sandwich elements together

How to Adapt This Steak Sandwich with Caramelized Onion, Mozzarella & Spicy Sauceto Your Diet

1. Keto-Friendly

• With low-carb bread: Use your Favorite keto-friendly, low-carb bread to enjoy the sandwich.
• Cottage cheese flatbread: Add the steak and toppings to cottage cheese flatbread. It’s easy to make and a delicious combination.
• Iceberg lettuce wrap: Wrap the steak and toppings in iceberg lettuce for a low-carb option.
• Without bread: Serve on a bed of arugula or greens with melted mozzarella over the hot steak, caramelized onions, capsicum, and diced tomatoes. (See instructions for the bread-free option).

2. Healthier Option:

• Serve with Sweet Potatoes For a heartier, healthier meal, serve the steak and toppings over or alongside roasted or mashed sweet potatoes. This option works for gluten-free, paleo, and dairy-free diets while adding nutritious carbs.

3. Gluten-Free

• Use gluten-free bread: Swap the low-carb sourdough for gluten-free bread.
• Without bread: Skip the bread and follow the bread-free option using arugula or greens, steak, mozzarella, and toppings.

4. Paleo-Friendly

• Without cheese: Omit the mozzarella for a strict paleo version. The steak, caramelized onions, capsicum, and spicy sauce will still provide plenty of flavor.
• Without bread: Serve on a bed of arugula or mixed greens, topped with steak, caramelized onions, capsicum, and diced tomatoes. (See instructions for the bread-free option).
• Iceberg lettuce wrap: Use iceberg lettuce instead of bread for a fresh paleo option.

5. Dairy-Free

• Omit the mozzarella: Leave out the mozzarella or use a dairy-free cheese alternative.
• Sauce: Ensure the mayonnaise is dairy-free or replace it with vegan mayo.

Why You’ll Love This Steak

This One Pan Fillet Steak Sandwich with Caramelised Onion, Capsicum, Cheese & Spicy Sauce is a culinary delight that you’re bound to fall in love with. Here’s why:

• Flavourful: Each ingredient is carefully chosen to create a symphony of flavours. The succulent steak, sweet and tangy caramelised onion and capsicum, creamy cheese, and hot, spicy sauce come together to create a truly unforgettable taste sensation.
• Versatile: Perfect for any meal of the day, whether it’s a quick midweek dinner, a weekend brunch, or a dish to impress at a gathering.
• Adaptable to Different Diets: This recipe can be easily customised to suit your preferences. Swap out the bread for gluten-free or low-carb options, or serve it without bread by using iceberg lettuce wraps or as a plated dish with the sauce, steak, and toppings.
• Balanced and Enjoyable Flavour: A harmonious blend of sweet, tangy, spicy, and savoury notes ensures each bite is satisfying and delicious.
• Super Tasty and Easy to Make: High in protein and simple to prepare using just one pan, making it ideal for both novice and experienced cooks.
• Diet-Friendly: This sandwich fits a variety of diets, including keto, paleo, gluten-free, and dairy-free options. For more ideas, check outthe section on How to Adapt This Fillet Steak Sandwich to Your Diet.

Steak Sandwich with Caramelized Onion, Mozzarella & Spicy Sauce

Annie, Healthy Food by Annie

This sandwich is packed with rich flavours and textures, combining succulent steak, sweet caramelised onions, and a creamy, spicy sauce. Perfect for keto, paleo, and gluten-free diets, it's a delicious high-protein meal that's easy and versatile for any occasion.

Print Recipe Pin Recipe

Prep Time 15 minutes mins

Cook Time 20 minutes mins

Cooling 10 minutes mins

Total Time 45 minutes mins

Course Breakfast, Lunch or Dinner

Cuisine Gluten-Free Option, High-Protein, Keto Option, Paleo Option

Servings 2

Ingredients

  

For the Steak:

• 2x 200 g fillet steaks
• 1 tablespoon butter
• 3 tablespoon avocado oil or olive oil
• 2 garlic clove
• 2 sprigs of rosemary
• ¼ teaspoon Salt and pepper

For the Caramelized Onions:

• 1 medium red capsicum, seeded and cut into thin strips
• 3 medium or 2 large onions, peeled, halved, and thinly sliced
• 1 small red chili, sliced into rounds
• ⅓ teaspoon oregano
• ½ teaspoon smoked paprika
• ¼ cup balsamic vinegar
• 1 tablespoon brown sweetener or honey
• 2 tablespoon avocado oil or olive oil

For the Sandwich:

• 1 small low-carb olive sourdough bread 
• 2 slices mozzarella (from a mozzarella ball)
• 1 tomato, sliced into rounds
• 2 bunches fresh rocket (arugula)

For the Sauce:

• ½ red chili, finely chopped
• 1 tablespoon olive oil mayonnaise
• 2 tablespoon reduced salt and sugar tomato sauce (ketchup)
• 1 te Dijon mustard
• 1 teaspoon oregano
• 1 teaspoon smoked paprika
• ⅓ teaspoon black pepper
• 1 teaspoon olive oil

Instructions

 

• Prepare the Sauce:

  In a small bowl, mix all the sauce ingredients well. Set aside.
• Caramelize the Onions and Capsicum:

  Heat 2 tablespoons of olive oil in a large skillet over medium-high heat. Add the capsicum, onions, chili, salt, and pepper. Cook for about 3 minutes, stirring occasionally. Lower the heat to medium-low, cover with a lid, and cook for another 5 minutes until soft and caramelized.

  Add Balsamic Vinegar and Spices: 

  Remove the lid and increase the heat to medium-high. Stir in the balsamic vinegar, sweetener (or honey), oregano, and smoked paprika. Cook, stirring frequently, until the vinegar reduces and thickens (about 5 minutes). Once done, transfer the caramelized mixture to a plate or bowl and set aside.
• Cook the Steak:

  Using the same skillet, add 3 tablespoons of olive oil and heat over medium-high. Add the fillet steaks, garlic, and rosemary. Cook for 2 minutes on one side, then flip the steaks and add the butter on top. Baste the steaks by spooning the butter and oil mixture over them as they cook.

  - If your steaks are thicker, cook for 3 minutes on each side to ensure a proper sear.

  - For well-done steaks, continue cooking for an additional 2 minutes per side, or until the steak reaches your desired doneness.

  Once done, transfer the steaks to a plate and slice thinly.
  
• Toast the Bread:

  Slice the sourdough bread horizontally into two halves. Spread butter on the inside of each piece and toast in the pan for about 2 minutes until golden. Remove from the pan.
• Melt the Cheese:

  Add the mozzarella slices to one half of the bread and return that half to the pan ( from cheese side down to pan) for 1 minute to melt the cheese. Alternatively, place both bread halves (with cheese) in the oven at 180°C (grill setting) for about 10 minutes, or until the cheese melts.
• Assemble the Sandwich:

  Spread some sauce on the other half of the bread. Top with rocket, caramelized onion, steak slices, more rocket, tomato slices, and additional caramelized onion.
  
• Complete the Sandwich:

  Place the cheesy half of the bread on top to complete the sandwich.
  
• Serve:

  Slice the sandwich into four pieces or your desired size and serve immediately.
  

For a bread-free option, follow these steps:

• Prepare the Plate:

  Use a serving plate or large platter and sprinkle a generous amount of fresh arugula (rocket) as the base.
• Add the Steak:

  Place the hot, thinly sliced fillet steak over the arugula.
• Melt the Mozzarella:

  Immediately place slices of mozzarella cheese over the hot steak to allow the heat to melt the cheese.
• Top with Caramelized Onions and Capsicum:

  Spoon the caramelized onions and capsicum over the rocket, steak, and cheese.
• Tomato Topping:

  Dice the tomatoes into small squares and drizzle them over the dish to add a fresh finish.
• Sauce:

  Drizzle the sauce over the dish or serve it on the side.

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Keyword Easy Recipe, One-Pan Meal