Preheat your oven to 375°F.
Roast the red bell pepper by placing it on a baking sheet, drizzling it lightly with olive oil, and roasting for about 15 minutes until the skin is slightly charred. Remove from the oven, let cool, then peel, deseed, and dice.
In a bowl, whisk together the 5 large eggs with a pinch of salt and pepper until the mixture is smooth and slightly frothy.
Heat a non-stick, oven-safe skillet over medium heat and add a drizzle of olive oil. Sauté the diced red onion until it becomes translucent, about 2-3 minutes.
Add the diced roasted red bell pepper to the skillet, stirring to combine with the onions.
Pour the egg mixture into the skillet over the vegetables, allowing it to settle evenly. Sprinkle the chopped fresh herbs evenly on top.
Allow the frittata to cook on the stovetop for about 3-4 minutes until the edges begin to set.
Transfer the skillet to the preheated oven and bake for an additional 8-10 minutes, or until the eggs are fully set and the frittata is slightly golden on top.
Remove from the oven, let it cool for a couple of minutes, slice, and serve warm.