In a bowl or zip-top bag, whisk together 3 tablespoons olive oil, 3 tablespoons lime juice, 3 minced garlic cloves, 1 teaspoon chili powder, 1 teaspoon smoked paprika, 1 teaspoon cumin, ½ teaspoon oregano, ½ teaspoon red pepper flakes (if using), and ½ teaspoon salt.

Add the 1½ pounds of steak to the marinade, ensuring it is well-coated. Refrigerate for at least 30 minutes (or up to 2-4 hours for deeper flavor).

When ready to cook, preheat a cast-iron skillet or grill pan over medium-high heat.

Remove the steak from the marinade and pat it dry. Cook the steak for about 4-5 minutes per side for medium-rare, adding additional time if you prefer it more well done.

Transfer the cooked steak to a cutting board and allow it to rest for 5 minutes to let the juices redistribute.

While the steak rests, add 1 tablespoon olive oil to the same pan and sauté the sliced bell peppers and onion until they are softened and slightly charred around the edges. Season with salt and pepper to taste.

Slice the rested steak against the grain into thin strips. Warm the tortillas and assemble your fajitas by layering steak, sautéed veggies, and your choice of optional toppings.