Preheat the oven to 375 F.Beat together the eggs with the salt and pepper (do not over-beat; just mix until the eggs mostly come together.) Stir in the grated cheeses and set aside. (Stir in hot sauce if using.)In a large oven-proof non-stick skillet, melt butter over medium-high heat. Add the onions and cook for several minutes, stirring frequently, until the onions are soft and golden brown. Add diced potato, sprinkle with salt and pepper, and stir to cook with the onion for a couple of minutes. Add the kale and stir to cook about 1 minute. Finally, add the roasted red peppers and olives and stir until everything is hot.Make sure all the ingredients are evenly distributed across the bottom of the skillet, then pour in the egg mixture so that it evenly coats everything. Let it sit on the burner for 30-45 seconds to set the edges, then put the skillet in the oven.Watch the frittata as it cooks. Let it cook in the oven for 10-12 minutes until the eggs are set but remove it before the eggs brown very much on top. Slide the frittata out of the skillet and onto a cutting board. With a long serrated knife, slice it into wedges and serve warm with fresh fruit. NOTE: Use any ingredients you want! Mushrooms, leeks, different cheeses, tomatoes, zucchini, squash, bell peppers. Have fun!