Creating a Spinach and Feta Frittata can be straightforward if you follow these simple steps:

1. Preheat Oven: Set your oven to 375°F (190°C).
2. Sauté Onion: In an oven-safe skillet, heat the olive oil over medium heat. Add the chopped onion and sauté until translucent, about 5 minutes.
3. Add Spinach: Stir in the chopped spinach and cook until wilted, around 2-3 minutes.
4. Beat the Eggs: In a bowl, whisk together the eggs, salt, black pepper, and red pepper flakes (if using).
5. Combine Ingredients: Pour the egg mixture over the sautéed spinach and onions in the skillet. Gently stir to evenly distribute the ingredients.
6. Add Feta: Sprinkle the crumbled feta cheese evenly across the top of the egg mixture.
7. Cook on Stovetop: Let the mixture cook on low heat for about 5 minutes, allowing the edges to set.
8. Transfer to Oven: Place the skillet in the preheated oven and bake for 15-20 minutes, or until the frittata is fully set and lightly golden on top.
9. Cool and Slice: Remove the skillet from the oven and let the frittata cool for 5-10 minutes before slicing.
10. Garnish: If desired, sprinkle with fresh parsley for a pop of color and flavor.

These steps will help you effortlessly create a delicious Spinach and Feta Frittata, allowing you to enjoy its amazing taste.