Tenderloin Steak Sandwich Recipe

Bring steak to room temperature

Remove the tenderloin steaks from the refrigerator 30 minutes before cooking so they come to room temperature. Pat dry with paper towels.

Season both sides of the steaks generously with kosher salt and freshly ground black pepper.

Heat a large heavy skillet (cast iron preferably) over medium-high heat until very hot, about 3–4 minutes. Add 1 tablespoon olive oil and swirl to coat.

Add the steaks and sear without moving 2–3 minutes until a deep brown crust forms. Flip and add 1 tablespoon butter, the smashed garlic clove and thyme sprig to the pan. Tilt the pan slightly and spoon the melted butter and aromatics over the steaks (baste) for another 2–3 minutes for medium-rare (internal temperature about 130–135°F / 54–57°C). Adjust time for desired doneness.

Transfer steaks to a cutting board and let rest for 5–7 minutes to allow juices to redistribute. When rested, slice thinly across the grain into 1/8–1/4-inch slices.

While the steak is resting (or concurrently), heat a medium skillet over medium heat. Add 1 tablespoon olive oil and 1 tablespoon butter until melted and shimmering.

Add the thinly sliced onion and red bell pepper to the pan, stir to coat. Sprinkle 1 teaspoon granulated sugar over the vegetables to help caramelize, and season with 1 teaspoon kosher salt and 1/2 teaspoon black pepper.

Cook, stirring occasionally, lowering heat slightly if the onions start to brown too fast, for 12–18 minutes until softened and deeply golden. In the last 1–2 minutes, add 1 teaspoon balsamic vinegar and stir to deglaze and concentrate flavor. Remove from heat and keep warm.

In a small bowl, combine 1/4 cup mayonnaise, 1 teaspoon Dijon mustard, 1/2 teaspoon Worcestershire sauce and 1/4 teaspoon garlic powder. Stir until smooth and adjust seasoning to taste.

If you prefer warm melted cheese: preheat oven broiler or a small salamander. Spread prepared mayo mixture evenly on the cut sides of the rolls. Top the bottom halves with a layer of sliced steak, then divide the caramelized onions and peppers over the steak. Top each sandwich with a slice or two of provolone or Swiss.

Place the open sandwiches under the broiler 1–2 inches from the heat for 1–2 minutes, watching closely, until cheese is melted and bubbly.

While cheese melts, spread the softened butter thinly on the cut side of the top roll halves and toast them in a skillet or under the broiler for 1–2 minutes until golden.

Remove sandwiches from broiler. If using, place a small handful (about 1/4 cup) of arugula or baby spinach on top of the melted cheese. Sprinkle chopped fresh parsley over the vegetables for brightness.

Close the sandwiches, press gently, slice in half if desired, and serve immediately.