Heat a skillet over medium-high heat. Lightly salt and pepper the steak. Place it on one side of the pan and the tomatoes, almonds, and garlic cloves on the other side.
Stir the tomatoes, almonds and garlic a few times until they brown evenly. After 3 minutes, flip the steak. Cook 2 minutes more and scoop the tomatoes, garlic and almonds into a food processor or blender. Keep the steak in the pan and continue to cook until done (thinly sliced steak will only need a few minutes more).
Add the roasted red pepper, olive oil, sherry vinegar and red pepper flakes to the food processor or blender and pulse until smooth.
Serve the Romesco sauce drizzled over the steak.
