Easy Vegetable Frittata

Preheat the oven to 375 degrees F. 2. Whisk the eggs, milk, salt, and pepper in a large bowl and set aside. 3. Heat olive oil in a medium oven-safe skillet over medium-high heat and cook the onion and bell pepper until softened, about 5 minutes. 4. Reduce the heat to medium-low, add the egg mixture, cover, and cook for 5 minutes. 5. Remove from the heat and top with the grated cheese and tomato slices. 6. Bake for 12-15 minutes until the cheese is melted.