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easy One Pan Fillet Steak Sandwich with Caramelized Onion, Mozzarella, and Spicy Sauce – Low-Carb Delight

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.
Prep Time 15 minutes
Cook Time 20 minutes
Cooling 10 minutes
Total Time 45 minutes
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
  • 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
  • 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.
    Step-by-step assembly of steak sandwich: spreading sauce, layering steak and caramelized onions
  • Complete the Sandwich:
    Place the cheesy half of the bread on top to complete the sandwich.
    Layering Fillet Steak, mozzarella, rocket, caramelised onion, and tomato on sourdough bread
  • Serve:
    Slice the sandwich into four pieces or your desired size and serve immediately.
    Medium-rare fillet steak layered with caramelized onions, mozzarella, tomato, arugula & Spicy Sauce

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.
Keyword Easy Recipe, One-Pan Meal
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