Place a burrito-sized tortilla on a flat service. Use scissors or a knife to make a cut from the bottom edge of the tortilla to the center.
Heat butter in nonstick skillet over medium-high heat. Whisk the eggs in small bowl, then carefully pour into the center of the pan. When the edges start to set, start to gently fold the eggs until the eggs are cooked through, about 2-3 minutes.
With the tortilla slit made, imagine the tortilla made up of four quarters. Transfer the scrambled eggs to the bottom right quarter.
Add the mashed avocado to the second quarter, followed by the salsa in the third and the cheese in the fourth.
Starting with the bottom right quarter, fold the tortilla over the second quarter, then over the third quarter and finally, over the last quarter to form a triangle shape.
Transfer the tortilla to the same skillet or a grill pan with a little extra butter for greasing. Cook the tortilla on one side pressing down firmly with a flat spatula, until golden brown and crispy, about 2-3 minutes. Flip and cook on the other side for 2 more minutes until the cheese is melty and the edges are crisp.
Remove from heat and allow to rest for one minute before slicing in half.
Notes
Storage: Store any leftovers wrapped tightly in foil in the fridge for up 2 days. To re-heat, you can heat it in a toaster oven or a skillet until the cheese is melted and the tortilla is heated through.