Combine the salt, cumin, garlic powder, oregano and black pepper. Rub over the steak.
Mash the avocado in a small bowl with the tomato, red onion, cilantro, lime juice, salt, pepper to taste. Set aside.
Combine the pico de gallo ingredients; set aside.
Heat a grill over high heat. Clean grates and spray with oil. Cook the steaks over high heat 2 to 3 minutes on each side, until the steak is cooked to your liking. Set aside on a cutting board to rest 5 minutes before slicing. Slice into thin strips.
To serve, fill each lettuce cups with 1 1/2 tbsp guacamole and top with steak and pico de gallo.