• Preheat the oven to 375°F. In a medium bowl, whisk together the eggs, milk, salt, and pepper until well combined. Heat olive oil in an oven-safe skillet over medium heat. Add the onion and garlic, sautéing until the onion is translucent, about 5 minutes.
• Add the spinach and cook until it’s just wilted, about 2 minutes. Scatter the cherry tomatoes and feta cheese (if using) evenly over the spinach.
• Pour the egg mixture into the skillet, making sure the eggs cover the vegetables evenly. Cook without stirring for about 2-3 minutes, until the edges begin to set. Transfer the skillet to the oven and bake for 15-20 minutes, or until the frittata is set and lightly golden on top.
• Remove from the oven and let it cool for a few minutes. Garnish with fresh herbs before slicing and serving.

Tip:

• Add other vegetables you have on hand, such as bell peppers, mushrooms, or zucchini, for a more filling and nutritious frittata. The frittata can be served hot, at room temperature, or even cold.