Place tomato, avocado and onion in a large bowl and add lime juice and salt. Add cilantro and chiles and toss gently.
Tacos
In a small bowl stir together cumin, garlic, salt and cayenne pepper. Rub spice mixture on both sides of steaks. Ideally, let marinate for at least 30 minutes. (you can marinate the steak while prepping the rest of the ingredients and the grill.)
Grill or broil steaks for 5 to 6 minutes on each side for medium rare, turning once. Remove from grill and let meat sit for 10 to 15 minutes. Carve into thin slices, slicing across the grain for the easiest eating.
Warm tortillas by placing them on the grill, for about 30 seconds, turning once. Or place 6 tortillas at a time between 2 moist paper towels and microwave for 45 seconds. Wrap in cloth napkin or place in a tortilla warmer to keep warm.
Place the carved steak, warm tortillas, cabbage, cilantro, lime and Avocado Salsa in serving dishes and let diners make their own tacos at the table.