For an extra layer of flavor, consider adding a sprinkle of red pepper flakes to the vegetable mixture. Feel free to substitute other vegetables based on your preference and what's in season. Zucchini, mushrooms, or spinach would be excellent additions. Ensure your cast iron skillet is well-seasoned to prevent sticking. If not, you may want to grease the skillet with additional bacon grease or oil before adding the egg mixture. Let the frittata cool slightly before slicing and serving. This will allow it to set properly.