Ingredients:

  • 1.5 lbs flank steak or skirt steak
  • 1 tsp salt
  • 1 tsp black pepper
  • 1 tsp garlic powder
  • 2 large yellow onions, thinly sliced
  • 3 tbsp unsalted butter
  • 1 tbsp olive oil
  • 2 tbsp dry white wine or balsamic vinegar
  • 1 tsp fresh thyme leaves
  • 6 oz Gruyère cheese, thinly sliced or shredded
  • 2 tbsp neutral oil
  • 2 tbsp cold butter

Instructions:

  1. Butterfly the steak by slicing horizontally through the center, stopping 1 inch from the edge. Place between parchment paper and pound with a meat mallet to 1/4 inch thickness.
  2. Season the entire surface of the beef evenly with salt, black pepper, and garlic powder.
  3. Heat olive oil and 3 tbsp butter in a skillet over medium heat. Add sliced onions and cook for 15–20 minutes until deep golden brown.
  4. Deglaze the onion pan with white wine or balsamic vinegar, stirring for 2 minutes until reduced to a glaze. Stir in fresh thyme and remove from heat.
  5. Spread a thin layer of caramelized onions over the steak, leaving a 1/2 inch border. Top with Gruyère cheese.
  6. Roll the steak tightly from the narrow end into a cylinder and secure with kitchen twine or toothpicks.
  7. Heat neutral oil in a cast iron skillet over medium-high heat. Sear pinwheels for 2–3 minutes per side until dark brown.
  8. Add cold butter to the pan and spoon the melted butter over the steak for 1 minute.
  9. Transfer the skillet to a 375°F (190°C) oven for 8–12 minutes until internal temperature reaches 130°F (54°C) for medium-rare.
  10. Let the meat rest for 5 minutes before slicing.