Frittata Recipe

Cook vegetables

Heat 2 tablespoons olive oil in a medium skillet over medium heat. Add the sliced red onion and cook, stirring occasionally, until softened and beginning to brown, about 8–10 minutes.

Add the sliced bell peppers and continue to cook over medium-low heat, stirring occasionally, until the peppers are very soft and starting to caramelize, about 15–20 minutes. If the pan becomes dry, add a splash of water (1–2 tablespoons).

Stir in the minced garlic and cook 1 minute more until fragrant. Add the tomato paste, red wine vinegar, and sugar; stir to combine and cook another 1–2 minutes to meld flavors.

Season with 1 teaspoon salt and 1 teaspoon freshly ground black pepper. Taste and adjust seasoning. Remove from heat and stir in chopped basil if using. Set aside about 1 to 1 1/2 cups of peperonata for the frittata filling (reserve remainder for serving). Let cool slightly.

Preheat oven to 425°F (220°C). Toss the halved or quartered mushrooms with 1 tablespoon olive oil, 1 teaspoon thyme, 1 teaspoon garlic powder, 3 teaspoons salt, and 1 teaspoon black pepper on a rimmed baking sheet in a single layer.

Roast until mushrooms are deeply browned and any released liquid has mostly evaporated, 15–20 minutes, tossing once halfway through for even browning. Remove from oven and let cool slightly.

Reduce oven temperature to 375°F (190°C). In a large bowl, whisk together 8 eggs and 1 cup milk or half-and-half until blended but not overly foamy. Whisk in 1 cup grated Parmesan, 1 teaspoon salt, and 1 teaspoon black pepper.

Heat a 10-inch ovenproof nonstick or well-seasoned cast-iron skillet over medium heat and add 1 tablespoon olive oil or butter, swirling to coat. Spread about half of the prepared peperonata evenly over the bottom of the skillet.

Scatter the roasted mushrooms evenly over the peperonata layer. Spoon the remaining peperonata in small dollops over the mushrooms so there are pockets of pepper flavor throughout.

Pour the egg-Parmesan mixture evenly over the vegetables, tilting the pan if needed so eggs settle around the pieces. Gently press any high bits down so the eggs can set evenly.

Cook on the stovetop over medium-low heat for 3–4 minutes until the edges start to set but the center is still loose. Transfer the skillet to the preheated 375°F (190°C) oven and bake 12–16 minutes, or until the frittata is mostly set and a knife inserted near the center comes out clean or with only a slight moistness.

If you prefer a browned top, switch to broil for 1–2 minutes, watching closely so it does not burn. Remove from oven and let rest 5 minutes; the frittata will finish setting as it rests.

Slice into 6–8 wedges, garnish with remaining grated Parmesan and chopped parsley or chives, and serve warm with any reserved peperonata on the side.