Begin by preparing the marinade. In a medium-sized bowl or shallow dish, combine the lime juice, olive oil, minced garlic, cumin, kosher salt, chili powder, black pepper, and cayenne pepper. Whisk everything together until the marinade is well-blended. Submerge the steak into the marinade, ensuring it is evenly coated. Cover the dish and refrigerate, allowing the steak to marinate for at least 1 hour and up to 4 hours for maximum flavor absorption.

When ready to cook, heat a large skillet over medium-high heat. Place the marinated steak into the hot skillet, allowing it to sear for 3 to 4 minutes on each side until a deep, flavorful crust forms. Once cooked to your preferred doneness, transfer the steak to a cutting board and let it rest for a few minutes to retain its juices.

As the steak rests, use the same skillet to heat the tablespoon of olive oil over medium-high heat. Add the sliced onions and bell peppers to the skillet, sautéing them for about 4 to 5 minutes. Stir frequently until the vegetables become tender and slightly caramelized.

After the steak has rested, slice it into long, thin strips, cutting against the grain for the most tender pieces. Return the sliced steak to the skillet with the sautéed vegetables. Toss everything together until well-mixed and heated through.

Serve the steak and vegetable mixture immediately with warm tortillas and your favorite toppings, such as creamy sour cream, fresh pico de gallo, rich guacamole, and a sprinkle of chopped cilantro. Enjoy your deliciously vibrant steak fajitas!