Preheat the oven to 400°F. In a large bowl, add the eggs, half-and-half, salt, and black pepper. Whisk everything together until the egg yolks and whites are well combined. Then stir in half of the shredded cheese.
Now heat a 10-inch cast iron skillet over medium heat. Add the olive oil, butter, diced bell peppers and onion. Sauté the veggies for 4-5 minutes until they have softened. Next add the chopped spinach along with a pinch of salt and pepper. Sauté for an additional minute and spread the vegetables around evenly in the skillet.
Next gently pour the egg mixture over the vegetables. Sprinkle the rest of the cheese over the skillet. Allow the frittata to cook on the stove for 2-3 minutes until the eggs start to barely set around the sides of the pan.
Now transfer the skillet to the preheated oven and bake for 15-17 minutes or until the eggs are set in the center.
Carefully remove the skillet from the oven and allow the frittata to rest for 5 minutes. It may be puffy once it comes out of the oven, but it will deflate while it rests. Garnish with fresh parsley or green onions (optional) and slice into wedges to serve. Enjoy!
Notes
I prefer white sharp cheddar cheese with this recipe, but if you can't find white cheddar feel free to use regular sharp cheddar cheese.
Feel free to swap out the vegetables in this recipe for a different combination. I've listed a few options in this post.
Storage: Frittatas store very well in the refrigerator and are perfect for meal prep! Just place any leftovers in an airtight container in the fridge for up to 4 days.