Preheat the Oven:

Preheat your oven to 375°F (190°C).

Sauté the Vegetables:

In an oven-safe skillet, heat olive oil over medium heat.

Add the diced onion and sauté for about 3-4 minutes, or until translucent.

Stir in the spinach and cook for another 2-3 minutes, until wilted. Remove from heat.

Prepare the Egg Mixture:

In a mixing bowl, whisk together the eggs, milk, salt, and pepper until well combined.

Stir in the shredded cheese and the sautéed vegetables.

Cook the Frittata:

Pour the egg mixture into the skillet over the cooked vegetables.

Let it cook on the stove for about 2-3 minutes until the edges start to set.

Bake in the Oven:

Transfer the skillet to the preheated oven.

Bake for 10-12 minutes, or until the frittata is puffed up and a toothpick inserted in the center comes out clean.

Cool and Serve:

Allow the frittata to cool for a few minutes before slicing. This will help it hold its shape.

Serve warm or at room temperature, garnished with fresh herbs if desired.

Variations

Add Veggies: Incorporate other vegetables like bell peppers, mushrooms, or zucchini for a heartier frittata.

Meat Lovers: Add cooked bacon, sausage, or ham for extra protein.

Herbs and Spices: Experiment with different herbs like basil, parsley, or thyme for added flavor.