This tart is simple, believe it or not; it just depends on patience and good ingredients. The onions need time to caramelize (that’s where most of the flavor comes from) and the crust needs to stay cold before baking so it turns out crisp instead of, well, tough. Once you get those two parts right, the rest will fall into place!
The goal is balance: buttery pâte brisée (french for a simple butter shortcrust pastry), slow-cooked onions, a layer of sliced apples arranged to look fancier than they are, and a gruyère melted across the top (and if you can get your hands on a smoked gruyère, even better!). Each bite should hit slightly sweet, definitely savory, and a little salty all at once. The thyme ties it together without taking over.
Tips and Tricks for Getting It Right!
Here are a few things to keep in mind so that this turns out perfect. We are not in the business of getting emotional over emotion-less objects and I just know you are going to pull this off with ease. In no specific order as I brain dump:
- Rest before slicing. Ten minutes out of the oven lets everything set into place so the slices stay clean when you go to serve.
- Use the right pan! A metal tart pan with a removable bottom gives better browning than ceramic or glass. If you only have a pie dish, bake a few minutes longer. This is the one I use.
- Keep the dough cold. The best shortcrust comes from cold butter, cold water, and cold hands. Warm butter makes crust dense and not that perfectly flaky texture. Chill the dough after mixing, after rolling, and even after pressing it into the pan if your kitchen is warm.
Note: This might just be why I like tarts in the winter I am realizing. - Blind bake. Don’t skip this step!! A quick bake with parchment and pie weights keeps the base from getting soggy once you add the filling. And if you don’t have pie weights, use dried beans; just make sure to be willing to sacrificed them since you can’t really eat them after cooking. I keep the dried beans I use in blind bakes in a ziplock and just use them over and over until they get realllllly dark. 🙂
- Repeat after me: Low and Slow on the onions. Caramelizing, and I hate to say this, but it takes 25–30 minutes. Essentially the time minimum on waiting for your dough to cool and relax in the fridge before rolling out. If you rush and cook on high heat, they’ll absolutely burn before turning sweet. Stir every few minutes on low heat and scrape up the brown bits as you go.
- Layer smart. Onions go first, then apples, then cheese. This keeps the bottom dry and ensures the cheese browns evenly. Plus, cheese on top means that your apples don’t have to look 100% perfect for it to turn out looking 100% perfect.
- Slice the apples thin. ⅛-inch slices look best and cook evenly. A mandoline helps if you have one, but I go freehand myself and with some patience in the slicing, it works just fine. Thin slices are key to pulling off the flower spiral look – too thick and they will resist / break in half when you put pressure on them to curve, especially as you get to the center and it gets tighter. And remember, it doesn’t have to be super perfect since we are covering with cheese!
This tart works hot, warm, or room temp for serving. Pair it with a simple arugula salad dressed in lemon or a bowl of roasted squash soup. Or on its own! For serving later, reheat at 350°F until just warmed through; I don’t really recommend microwaving because you’ll lose the crisp crust, but you do you at the end of the day. Any leftovers can be wrapped and refrigerated for up to 3 days, and leftovers make for a fantastic breakfast with your morning coffee or tea!
Savory Apple + Caramelized Onion Tart
Equipment
- Tart pan (with removable bottom!)
- Rolling Pin
- skillet
- Parchment paper
- Pie weights or dried beans; If using, don't cook to Eat after
Ingredients
For the Pâte Brisée:
- 1 ¼ cups all-purpose flour
- ½ teaspoon salt
- ½ cup 1 stick cold unsalted butter, cut into cubes Or Plant Based Butter for Vegan Version
- 3 to 4 tablespoons ice water
For Tart Filling:
- 2 large yellow onions thinly sliced
- 1 tablespoon olive oil
- 1 tablespoon butter Or Plant Based Butter for Vegan Version
- 1 teaspoon salt
- 1 teaspoon sugar
- 2 sprigs fresh thyme leaves removed (plus extra for garnish!)
- 1 tablespoon balsamic vinegar optional but recommended for depth
- 1-2 large apple OR 3 small apples, thinly sliced
- ½ cup shredded Gruyère or plant-based cheese, thinly Shredded Best
- Freshly cracked black pepper
Instructions
- In a large bowl, whisk together flour and salt. Cut in the butter using a pastry cutter or fingers until coarse crumbs form. Add ice water, one tablespoon at a time, mixing gently until the dough just comes together. Form into a disk, wrap, and chill for 30 minutes.
- Preheat oven to 375°F (190°C). Roll out chilled dough on a lightly floured surface to fit your tart pan. Press into pan, trim edges, and prick the base with a fork. Line with parchment, fill with pie weights, and blind bake for 15 minutes. Remove weights and bake another 5 minutes until lightly golden.
- In a large skillet over medium heat, melt butter and oil. Add sliced onions, salt, and sugar. Cook slowly, stirring occasionally, until deeply golden and soft, about 25–30 minutes. Add thyme leaves and balsamic vinegar (if using), stirring for another minute. Remove from heat.
- Spread caramelized onions evenly over the baked crust. Layer the apple slices over top in a circular pattern. Sprinkle with cheese and a few extra thyme leaves.
- Bake at 375°F for 20–25 minutes, until apples are tender and cheese is lightly browned.
- Let cool slightly before slicing. Finish with cracked black pepper and a few fresh thyme leaves. Serve warm or room temperature.