Combine marinade: In a bowl, whisk together 2 tbsp olive oil, 2 tbsp freshly squeezed lime juice, 1 tsp cumin, 1 tsp chili powder, 1 tsp garlic powder, 1 tsp salt, and 1/2 tsp black pepper. Add the 1 lb flank steak (or skirt steak) and coat well. Marinate for at least 30 minutes or up to 2 hours for maximum flavor.
Preheat grill: Set your grill or skillet over medium-high heat. Remove the marinated steak from the bowl and cook it for about 4-5 minutes on each side for medium-rare. Let it rest for 5 minutes before slicing to keep it juicy.
Sauté vegetables: In the same skillet, toss in the sliced red and green bell peppers along with the sliced onion. Sauté them for about 5-7 minutes until they are softened and slightly charred, enhancing their natural sweetness.
Slice steak: After resting, slice the steak against the grain into thin strips for tender bites. Serve these delightful strips alongside the sautéed vegetables on warm flour tortillas with your favorite toppings—like sour cream, guacamole, shredded cheese, and fresh cilantro.