Place the top rack of the oven about 6 inches (15 cm) from the broiler element. Preheat the oven to broil.
In a large bowl, whisk together the eggs, taco seasoning, salt, pepper and cilantro. Set aside.
In a 10 inch (25 cm) oven-proof skillet, heat the olive oil over medium heat. Add the green onions, black beans, red peppers, potatoes and jalapeno (if using) to the skillet, stirring until heated through.
Pour the egg mixture into the pan; stir to combine with the vegetables and beans. Use a spatula to gently distribute the vegetables evenly within the skillet and then leave the eggs undisturbed to set on the bottom, about 2 minutes. Reduce the heat to medium-low and cook the frittata gently for about
8 minutes until the eggs are almost set on top, but still moist. Sprinkle the cheese on top.
Place the skillet under the broiler. Broil for 1 to 2 minutes, watching carefully, until the cheese is melted and the eggs are just set. Let frittata stand for 3 minutes before serving.
Run a spatula around the edge of the frittata and gently shake the skillet to loosen the frittata. Slice into wedges and serve with optional toppings of your choice.