Heat a large skillet with butter over medium-high heat. Add the well-whisked eggs to the skillet. Season with sea salt and freshly cracked black pepper to taste.
Constantly fold the egg mixture from the bottom of the skillet to the top. This will keep them from overcooking, and the middle section will stay soft and fluffy. Do this constantly for 1 or 2 minutes, or until the eggs are set. Do not overcook. Remove from heat.
Meanwhile, heat the black beans and corn in the microwave until hot, about 20 seconds.
Heat the tortilla for a few seconds over a flame on a gas stove, or in a dry large skillet, until pliable. Side Note: You can also wrap a tortilla in a dish towel, then place it into the microwave for 20 seconds or until warm and pliable.
Place the beans and corn down the center of the warm tortilla, then top with the scrambled eggs, slices of avocado, tomato, green onion, cotija cheese, and fresh cilantro.
Roll into a burrito, then place on a plate seam side down.