1
Preheat the oven to 350 degrees. Heat the olive oil in a large cast iron skillet (or oven-proof skillet) over medium heat.
2
Add the onion, red bell pepper, and broccoli and sprinkle with 1/2 teaspoon of the salt. Cook and stir for 5 minutes, then reduce the heat to low and cover with a lid. Cook for 5 more minutes, or until the veggies are tender. Add the garlic and cook until fragrant, about 30 seconds.
3
Whisk the eggs with warm water. Add in the rest of the salt, black pepper, cheddar cheese, and 1/4 cup of Parmesan cheese.
4
Pour the egg mixture over the vegetables in the skillet and give it a quick stir. Cook for about 5 minutes, or until the eggs begin to set along the pan's edge.
5
Sprinkle the remaining Parmesan cheese, red bell pepper rings, and crushed red pepper flakes on top. Remove from the heat and place the frittata in the preheated oven. Bake for 12 to 15 minutes, until the eggs are just set with a slight jiggle in the middle.
6
Place the frittata under the broiler for a couple of minutes to brown the top, if desired. Cut into wedges and serve.
