Preheat the oven to 350°. Warm the tortillas. Heat 1 (16-ounce) can of beans in a small saucepan. Melt 2 tablespoons butter in a large nonstick skillet. Fry the eggs to the desired degree of doneness. Slightly overlap 2 tortillas on a warm plate. Place 2 tablespoons salsa, 1/3 cup beans, and 1 egg in the center of each plate. Garnish with salsa, sour cream, and avocado. Repeat the process with remaining ingredients.