How to Make the Perfect French Onion Frittata
French · Medium · 50 min · 6 servings
This sophisticated oven-finished frittata is loaded with deeply caramelized sweet onions and melted Gruyere cheese, drawing all the beloved flavors of classic French onion soup into a hearty egg dish. It is ideal for feeding a crowd at brunch and can be served warm or at room temperature.
Why this recipe works
This French Onion Frittata recipe has been crafted to deliver restaurant-quality results in your home kitchen. At just 50 minutes from start to finish, it fits perfectly into a busy schedule without sacrificing flavor. Each serving comes in at 290 calories with 17g of protein, making it a balanced choice for any meal.
What you will need
This recipe uses 6 simple ingredients that you can find at any grocery store:
- 3 whole large yellow onions thinly sliced
- 8 whole large eggs
- 1 cup shredded Gruyere cheese
- 2 tablespoons unsalted butter
- 0.25 cup whole milk or heavy cream
- 1 teaspoon fresh thyme leaves
Step by step instructions
Step 1: Caramelize the Onions
Melt butter in a 10-inch oven-safe skillet over medium-low heat and add the sliced onions with a pinch of salt. Cook slowly, stirring every few minutes, for 30 to 35 minutes until the onions are deeply golden, sweet, and jammy. Do not rush this step as it builds the core flavor.
Step 2: Prepare the Egg Mixture
Preheat your oven to 375 degrees. Whisk together the eggs, milk, fresh thyme, salt, and a generous amount of black pepper in a large bowl until fully combined and slightly frothy. Stir in half of the shredded Gruyere and set aside.
Step 3: Cook the Frittata Base
Spread the caramelized onions evenly across the bottom of the skillet over medium heat. Pour the egg mixture over the onions and gently stir to distribute everything evenly. Cook undisturbed for 3 to 4 minutes until the edges begin to set but the center is still jiggly.
Step 4: Finish in the Oven
Scatter the remaining Gruyere cheese over the top of the frittata and transfer the skillet to the preheated oven. Bake for 10 to 12 minutes until the center is fully set and the top is lightly golden and puffed. Let rest for 5 minutes before slicing into wedges.
Easy substitutions
Missing an ingredient? Here are some swaps that work perfectly:
- Gruyere cheese → Swiss cheese or aged white cheddar for a similar nutty flavor
- yellow onions → shallots and leeks combined for a more delicate flavor
Common mistakes to avoid
Watch out for these pitfalls that can affect your results:
- Rushing the caramelization step by cooking onions on high heat which makes them bitter instead of sweet
- Overcooking the frittata in the oven resulting in a rubbery dry texture
Nutrition facts
Per serving: 290 calories, 17g protein, 12g carbs, 19g fat, 2g fiber.
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