In a bowl, whisk eggs with salt and pepper until well combined.
Heat olive oil in an oven-safe skillet over medium heat.
Add chopped onions, mushrooms, and broccoli to the skillet. Sauté for 3–5 minutes until softened.
Pour the whisked eggs over the sautéed vegetables. Quickly scrape the sides and stir gently to distribute evenly.
Remove from the stovetop and transfer the skillet to the oven.
Bake for 5–8 minutes or until the eggs are fully set and slightly golden on top.
Remove from the oven and let cool for 1–2 minutes before slicing.
Serve with sliced apple on the side.
Notes
Other varieties: Use other vegetables such as bell peppers, spinach or squash
More Flavor: Add cheese, salsa, or fresh herbs to eggs
Protein content: ~ 18 g per serving when divided into 2 servings; for more protein, add meat to the frittata or enjoy with a ½ cup Greek yogurt