Preheat your oven to 375°F (190°C).
In a large bowl, whisk together eggs, milk, salt, and pepper until well combined. Set aside.
Heat olive oil in a 10-inch oven-safe skillet over medium heat. Add onion and bell pepper and sauté for 5 minutes until softened.
Add garlic and cook for 30 seconds until fragrant. Stir in spinach and cook until wilted, about 2 minutes.
Spread vegetables evenly across the bottom of the skillet. Scatter cherry tomatoes on top.
Pour the egg mixture over the vegetables, gently tilting the pan to distribute evenly. Sprinkle shredded cheese over the top.
Cook on the stovetop for 3-4 minutes until edges begin to set.
Transfer the skillet to the oven and bake for 15-18 minutes, until the center is set and the top is lightly golden.
Let cool for 5 minutes, then slice into wedges and serve warm. Great with toast or a simple side salad!