Save to Pinterest This Caramelized Onion and Gruyere Tart is the answer when I want something a little fancy but deeply comforting—a savory, flaky pastry bursting with golden sweet onions and nutty Gruyere. Whether for brunch, a light dinner, or as a show-stopping appetizer, it wins over everyone at the table every single time.
I first made this for a holiday brunch, and the way the onions melted into the rich cheese turned my house into a French bistro for a morning. The tart always disappears fast whenever I serve it, and even the skeptics ask for seconds.
Ingredients
- Puff pastry sheet: about 250 grams because this provides a buttery yet crisp base for the tart and look for pastry made with butter for best flavor
- Unsalted butter: for rich flavor and browning the onions
- Olive oil: to balance the butter and help onions caramelize evenly
- Large yellow onions: thinly sliced as their natural sweetness is the star
- Sugar: just a bit to help the onions develop deep color and sweetness as they cook
- Salt and freshly ground black pepper: to balance sweetness and round out the flavor
- Fresh thyme leaves or dried thyme: as this herb brings classic French taste choose fresh if you can for more aroma
- Gruyere cheese: grated which melts beautifully and brings nutty pungency to the tart select a wedge you grate yourself to avoid pre-shredded dryness
- Eggs: to bind the filling and add structure and creaminess
- Heavy cream: because it brings a custard-like richness to the filling choose one labeled as double or heavy for the silkiest texture
- Ground nutmeg: just a pinch to add warmth in the background freshly grated if possible
Instructions
- Prepare the Oven:
- Preheat the oven temperature to 200 degrees Celsius or 400 degrees Fahrenheit so the crust bakes up golden and even
- Shape and Chill the Pastry:
- Roll out the thawed puff pastry on a lightly floured surface until it fits a nine inch tart pan Press the pastry into the pan trim any overhang and prick the base with a fork This prevents bubbling Place the pan in the refrigerator to keep the pastry cold while you make the filling this ensures maximum flakiness
- Caramelize the Onions:
- Heat both the butter and olive oil together in a large skillet on medium heat Add the sliced onions sugar salt and pepper Cook stirring every few minutes so nothing burns For about twenty five to thirty minutes the onions will slowly turn soft golden and sweet Turn the heat a bit lower if they start browning too quickly In the last five minutes stir in the thyme leaves The onions should become meltingly tender and deeply brown Let them cool slightly before using
- Prepare the Filling:
- In a separate bowl whisk the eggs with cream nutmeg salt and pepper until fully blended The result should be smooth and creamy with specks of nutmeg floating throughout
- Fill the Tart:
- Spoon the cooled caramelized onions evenly across the chilled pastry in the pan Sprinkle all of the grated Gruyere cheese over the onions For the finishing touch pour the egg and cream mixture over everything gently tilting the pan if needed so it covers the surface
- Bake:
- Place the tart on the middle rack of your oven Bake for thirty to thirty five minutes until the pastry is puffed the filling is golden and firm and the cheese is gloriously melted Let it cool for at least ten minutes This makes for neater slices and a creamy set center
- Serve:
- Slice into wedges and serve warm or at room temperature This tart makes a perfect addition to a picnic spread or a hearty weekend brunch
Save to Pinterest My favorite part is the way Gruyere forms little golden bubbles on top The first time I made this my son declared It smells like Paris in here and now we always joke that the kitchen turns into a French bakery on tart day
Storage Tips
Refrigerate leftovers tightly covered and enjoy within three days The crust stays crisp if you reheat slices in the oven instead of the microwave For longer storage you can freeze individual slices wrapped in foil Just reheat from frozen at a moderate oven temperature until heated through If you have a large crowd double the recipe and prepare two tarts they hold up perfectly for make-ahead entertaining
Ingredient Substitutions
If Gruyere is tricky to find Emmental or regular Swiss cheese work well Cheddar brings a sharper bite if you want to switch things up Puff pastry can be swapped for a shortcrust shell if you crave a different texture For an herby touch add a sprinkle of chopped fresh rosemary or chives in with the onions
Serving Suggestions
Pair the tart with a lemony green salad or peppery arugula for balance Add a chilled glass of dry white wine for a true French bistro vibe This also makes a fantastic centerpiece for brunch with a side of lightly dressed tomatoes
Cultural Context
This tart hails from French bistro cuisine a classic blend of humble ingredients turned into something elegant The marriage of caramelized onions and nutty Gruyere is found in French onion soup too so if you love that rich savory flavor you will find this tart comforting and satisfying
Seasonal Adaptations
In the spring try adding asparagus tips chopped into the onions In fall swap in half red onions or a handful of sautéed wild mushrooms Zucchini ribbons can be layered in for a fresh summer take
Save to Pinterest Serve this tart for brunch or a cozy dinner and watch it disappear slice by slice It is the kind of recipe that feels special but is secretly simple to make
Common Recipe Questions
- → What makes the onions taste sweet and golden?
Slowly cooking the onions with butter, olive oil, and a touch of sugar over low heat allows them to caramelize, bringing out their natural sweetness and golden color.
- → Can I substitute Gruyere cheese?
Yes, Emmental or Swiss cheese are good alternatives that offer a similar nutty flavor and melt beautifully.
- → How do I keep the pastry crisp?
Chill the rolled pastry before baking and avoid over-filling with wet ingredients. Pricking the base helps prevent sogginess.
- → Is it suitable for vegetarians?
Yes, this tart uses only plant-based ingredients and dairy, making it suitable for a vegetarian diet.
- → What can I serve alongside the tart?
A crisp green salad and a glass of dry white wine pair beautifully, enhancing the flavors and freshness of the dish.
- → Can I prepare it ahead of time?
Yes, the tart can be baked and allowed to cool, then served at room temperature or gently reheated before serving.