Mix all the spices with the oil and lemon juice, and rub onto both sides of the meat. Let it marinate for 1 hour at room temperature. If it's very hot, place it in the refrigerator.

Grill the meat on a very hot grill. Cook to your preferred doneness. Let it cool, then slice thinly against the grain. Slice when cold so the meat stays juicy and doesn't dry out.

Heat the oil in a skillet and sauté the onion with the garlic. Add the bell peppers, oregano, cilantro, salt, and pepper to taste. Cook for 2 minutes. Add the meat, mix, and heat gently.

Serve with small bowls of pico de gallo, guacamole, and sour cream.