If you’re craving something cozy, savory, and a little bit gourmet without spending hours in the kitchen, say hello to your new favorite: the French Onion Frittata. It’s the perfect marriage of two timeless classics—French onion soup and a fluffy frittata—delivering big flavors with little effort.
Whether you’re planning an elegant brunch, a hearty breakfast, or a meatless dinner that satisfies, this dish fits right into your routine. With just a few pantry staples like eggs, onions, cheese, and broth, you’ll be able to transform humble ingredients into something memorable and mouthwatering. And the best part? This one-skillet wonder is easy to make, easy to reheat, and impressively delicious.
🍽️ Why You’ll Love This French Onion Frittata
This isn’t just any egg dish. It’s layered, luxurious, and guaranteed to convert even the biggest skeptics of vegetarian recipes.
Here’s why you’ll keep coming back to it:
- Inspired by a Bistro Favorite: Think of all the best parts of French onion soup—the sweet, golden onions, savory broth, and melted cheese—now imagine them in a fluffy, sliceable form.
- Minimal Ingredients, Maximum Flavor: You don’t need a grocery haul. Simple kitchen staples shine here.
- Perfect for Any Meal: Serve it hot for dinner, cold for lunch, or reheat for breakfast.
- High in Protein, Low in Carbs: Great for gluten-free and low-carb lifestyles.
- Elevated Comfort Food: This recipe feels gourmet but is grounded in home-style ease.
🛒 Ingredients Breakdown
Let’s take a look at the building blocks of this beautiful dish.
🧈 Unsalted Butter
The start of every good caramelized onion is fat. Unsalted butter allows you to control the flavor. For deeper flavor, you can blend with a touch of olive oil.
🧅 Yellow Onions (2 large)
Yellow onions are ideal for caramelization thanks to their balance of sweetness and acidity. Thinly sliced is key—they’ll reduce in volume by more than half.
🧂 Kosher Salt & Fresh Black Pepper
Basic seasoning but essential. Kosher salt absorbs better during cooking. Fresh black pepper adds dimension.
🍲 Low-Sodium Chicken or Vegetable Broth (¼ cup)
Used to deglaze the pan, lift those flavorful bits from the skillet, and add a savory note that mimics French onion soup.
🥚 Large Eggs (8 total)
Eggs are the heart of any frittata. Choose fresh, organic if possible for better rise and taste.
🥛 Whole Milk (¼ cup)
Adds a creamy texture to the eggs. You can substitute with cream for a richer taste or plant milk for dairy-free needs.
🥄 Dijon Mustard (1 tablespoon)
The unsung hero of this recipe. It cuts through the richness, adds brightness, and enhances the umami depth.
🧀 Gruyère Cheese (1 cup, shredded)
Nutty, melty, and elegant. Gruyère makes this dish shine. Swap with Swiss or Fontina if needed.
🌿 Fresh Thyme (optional)
Aromatic and earthy, thyme balances the sweetness of onions with its herbal flair.
🔥 How to Caramelize Onions (Without Burning Them)
The magic of French onion anything lies in the onions—and how you caramelize them.
Here’s how to do it right:
- Use a wide skillet: More surface area equals better browning.
- Cook low and slow: Medium-low heat for 25–30 minutes. Don’t rush.
- Stir occasionally: Every 5 minutes is ideal. You want browning, not burning.
- Deglaze with broth: Once golden, a splash of broth releases all that umami from the skillet base.
✅ Pro Tip: You can make caramelized onions in advance and store in the fridge for up to 5 days.
👩🍳 Step-by-Step French Onion Frittata Instructions
🕒 Total Time: 50 minutes | Servings: 6 slices
Step 1: Preheat and Prep
Preheat your oven to 400°F (200°C). Set your oven-safe skillet over medium heat.
Step 2: Caramelize the Onions
Melt 2 tablespoons of butter. Add sliced onions, a pinch of salt, and black pepper. Cook for 25–30 minutes until deep golden brown. Stir occasionally. Once done, pour in the broth and simmer for 1–2 minutes.
Step 3: Whisk the Egg Mixture
In a large mixing bowl, combine eggs, milk, Dijon mustard, and half of the shredded cheese. Whisk until smooth.
Step 4: Combine and Bake
Pour the egg mixture into the skillet over the onions. Stir gently to distribute. Sprinkle the rest of the cheese on top.
Transfer the skillet to the oven and bake for 15–18 minutes until the frittata is puffed and golden.
Step 5: Rest and Serve
Let it cool for 5 minutes. Garnish with fresh thyme. Slice and serve.
🌿 Variations and Add-ins
Want to customize your frittata? Here are some tested variations:
| Ingredient | Flavor Boost |
|---|---|
| Mushrooms (sautéed) | Earthy richness |
| Spinach (chopped) | Color + nutrients |
| Bacon or pancetta | Smoky, salty balance |
| Goat cheese | Tangy creaminess |
| Roasted garlic | Intensified savory depth |
🔧 Expert Tips for Frittata Success
- Use fresh eggs for fluffier texture and better rise.
- Let onions cool slightly before adding egg mixture to prevent curdling.
- Use an oven-safe skillet to avoid transferring to a baking dish.
- Don’t overbake. Remove when the center is just set for a soft, creamy texture.
- Always rest before slicing. This helps the structure firm up without collapsing.
🕰️ Make Ahead and Meal Prep Instructions
This frittata is a meal prep champion.
To make ahead:
- Cook completely, let cool, slice, and store in airtight containers.
- Reheat slices in the microwave (covered with damp paper towel) or air fryer (350°F for 4–5 minutes).
For freezing:
- Wrap individual slices in plastic wrap and freeze in zip bags.
- Thaw overnight and reheat in oven or toaster oven.
🧊 Storage and Reheating Tips
| Storage Method | How Long | Best Reheat |
|---|---|---|
| Fridge | 4 days | Microwave or skillet |
| Freezer | 2 months | Oven or air fryer |
🧾 What to Serve With French Onion Frittata
Balance your plate with these side ideas:
- Fresh arugula salad with lemon vinaigrette
- Crusty bread or garlic toast
- Sautéed green beans or asparagus
- Roasted baby potatoes
- Fresh fruit and yogurt for brunch pairings
❓ Frequently Asked Questions (FAQs)
Can I make this dairy-free?
Yes! Use olive oil instead of butter, non-dairy milk, and a vegan cheese alternative.
Can I use red onions instead?
You can, but they may not caramelize as sweetly as yellow onions. Expect a slightly different flavor profile.
What if I don’t have Gruyère?
Swiss, Fontina, or a mix of mozzarella and Parmesan work in a pinch.
Can I double the recipe?
Yes, but use a larger baking dish or two skillets and increase baking time by 5–10 minutes.
🖨️ Printable French Onion Frittata Recipe
French Onion Frittata – A Classic Twist on Easy Recipes for Dinner
Prep Time: 10 mins
Cook Time: 40 mins
Total Time: 50 mins
Servings: 6 slices
Ingredients:
- 2 tbsp unsalted butter
- 2 large yellow onions, thinly sliced
- ½ tsp kosher salt
- ¼ tsp ground black pepper
- ¼ cup chicken or vegetable broth
- 8 large eggs
- ¼ cup whole milk
- 1 tbsp Dijon mustard
- 1 cup shredded Gruyère cheese, divided
- Fresh thyme (optional)
Instructions:
- Preheat oven to 400°F.
- In an oven-safe skillet, melt butter and caramelize onions with salt and pepper for 25–30 mins.
- Add broth and simmer for 2 mins.
- In a bowl, whisk eggs, milk, mustard, and half of the cheese.
- Pour egg mix over onions. Stir gently. Top with remaining cheese.
- Bake 15–18 mins until puffed and golden.
- Let rest 5 mins. Slice and serve with thyme.
🧮 Nutrition Info (Per Slice)
- Calories: 210
- Protein: 12g
- Carbohydrates: 7g
- Sugar: 3g
- Fat: 15g
- Saturated Fat: 6g
- Cholesterol: 210mg
- Sodium: 320mg
- Fiber: 1g
