Step 1

Preheat the oven to 375°F.

Step 2

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

Step 3

Heat the olive oil in an oven-safe skillet over medium-high heat. Add the diced onion and sauté until softened, about 5 minutes.

Step 4

Add the spinach leaves to the skillet and sauté until wilted, about 2-3 minutes.

Step 5

Pour the egg mixture into the skillet and gently stir to combine with the spinach and onions. Cook for 2-3 minutes until the eggs start to set.

Step 6

Arrange the halved cherry tomatoes on top of the egg mixture, then sprinkle with shredded cheddar cheese.

Step 7

Transfer the skillet to the oven and bake for 15-20 minutes, or until the frittata is set and the cheese is melted and golden brown.

Step 8

Remove from the oven and let it cool for a few minutes before slicing and serving.