Preheat the Oven : Preheat your oven to 375°F (190°C).

Cook the Vegetables : Heat the olive oil in an oven-safe, non-stick skillet over medium heat. Add the broccoli, red bell pepper, and red onion to the skillet. Cook, stirring occasionally, for 5-6 minutes or until the vegetables are slightly softened. Season with a pinch of salt and pepper.

Prepare the Egg Mixture : In a medium bowl, whisk together the eggs and egg whites until well combined. Stir in half of the shredded cheddar cheese. Season with a little more salt and pepper, if desired.

Assemble the Frittata : Spray the edges of the skillet with cooking spray to ensure the frittata doesn’t stick. Pour the egg mixture evenly over the cooked vegetables in the skillet. Sprinkle the remaining cheddar cheese on top.

Bake the Frittata : Transfer the skillet to the preheated oven and bake for 15-18 minutes, or until the frittata is set in the center and lightly golden around the edges. Remove from the oven and let it cool for 2-3 minutes.

Garnish and Serve : Slide the frittata out of the skillet and onto a cutting board or serving plate. Garnish with fresh herbs, such as cilantro, parsley, or green onions. Slice into wedges and serve warm.