Toss diced tomatoes, onion, peppers, cilantro, olive oil, lemon or lime juice and salt and pepper in a medium-sized bowl then refrigerate while you make the tacos.
Heat a large, non-stick skillet over medium-high heat. Add a tiny bit of olive oil to the bottom of the pan. Place two or three tortillas to the skillet and allow them to brown slightly—approximately 2 minutes. Flip them over to brown on the other side. When browned, transfer to a plate, separating them with paper towels. Add a tiny bit more oil to the pan then repeat until all tortillas have been browned.
Build your tacos, one at a time, layering the shredded beef, lettuce, cheese, avocado and pico de gallo to your liking. Spritz with lime juice, serve with your favorite accompaniments such as a corn and black bean salad, Spanish noodles or cilantro lime rice.
Notes
When choosing an avocado, look for one that has a black, pebbly skin. It shouldn’t be too soft or too firm.