Mash the avocado with a pinch of salt and lime juice, leaving it slightly chunky.
Whisk the eggs with a pinch of salt. To a non-stick skillet, over medium-high heat, add the butter. When the butter is melted, add the whisked eggs. As soon as they start to set on the edges, push them to the center using a rubber spatula and fold over. Cook until the eggs are set but still a bit wet/runny.
Warm up the tortillas. Stack them on a plate and cover with a damp paper towel. Microwave for about 1 minute on full power until the tortillas are soft. See in the note 4 how to warm them up in the oven, in a cast-iron pan, or directly over the flame.
Serve everything ready for everyone to assemble their own tacos: warm tortillas (you can wrap them up in foil to keep them warm), mashed avocado, scrambled eggs, smoky salsa, grated cheese, fresh cilantro, crispy bacon (optional).
To build the taco, put a bit of cheese on first, then scrambled eggs, then a bit more cheese, mashed avocado, crispy bacon, smoky salsa, and some fresh cilantro.