Preheat broiler. In a bowl whisk together eggs, cheese, cilantro, salt, and black pepper. In a large broiler-proof skillet cook sausage, onion and red sweet pepper in hot oil over medium heatabout 5 minutes or until vegetables are crisp-tender, stirring occasionally. Stir in beans.
Pour egg mixture over vegetables in skillet. Cook over medium heat. As mixture sets, run a spatula around edge of skillet, lifting egg mixture so uncooked portion flows underneath. Continue cooking and lifting edges until egg mixture is almost set (surface will be moist).
Place skillet under broiler 4 to 5 inches from heat. Broil 1 to 2 minutes or until top is set. Let stand5 minutes. Slide frittata onto a serving platter. Sprinkle with tomato. Cut into wedges. If desired, top with avocado and sour cream.