In a large bowl, add 2 tablespoons olive oil, steak, 1/2 lime juice, red pepper flakes and sea salt and freshly ground pepper to taste and cover to marinate in the refrigerator for at least 20 minutes (or use large zipper topped plastic bag instead of bowl and cover).
On an indoor grill, heat 1 tablespoon olive oil over medium heat and grill peppers and onions for 5 to 7 minutes per side.
Remove steak from marinade. Add steak to vegetables on the grill and grill 3 to 5 minutes per side until steak is cooked through. Place steak in tortilla and top with bell peppers and onions, cilantro, lime juice and avocado.