In a medium skillet, heat butter over medium heat. Add beans, peppers and onions; salt and pepper to taste. Sauté until peppers are softened (about 2-3 minutes).
In medium bowl whisk eggs and cumin; salt and pepper to taste. Add to skillet; allow egg mixture to begin setting; slowly pull spatula across egg mixture occasionally, allowing uncooked eggs to run under cooked eggs.
Remove from heat and stir in cheese and avocado. Divide mixture between 2-3 tortillas; fold up burrito style. Serve with sour cream and salsa, if desired.