Preheat your oven to 400°F.
Place your cast iron pan over medium heat as you prepare your ingredients.
Combine your frittata base. Whisk the eggs, water, milk, garlic, salt, and pepper. It’s ready when it is a consistent light-yellow color throughout.
Sauté your chosen vegetables in your fat of choice in the preheated cast iron skillet. Cook stirring occasionally, just until they are tender.
Add any spices or herbs you are using.
Spread the vegetables evenly over the surface of your cast iron, then pour the frittata base over your vegetables, shaking the pan gently to distribute the eggs evenly.
Sprinkle your cheese on top of the frittata and transfer the pan to a 400°F oven.
Bake for 15-20 minutes until the center is set and the top and edges are golden.
Allow the frittata to cool for 15-20 minutes before slicing. Enjoy!