Few dishes capture the essence of autumn cooking quite like a Caramelized Onion & Squash Tart. Rich, slow-cooked onions meet sweet, tender squash in a flaky crust, creating a dish that feels both elegant and deeply comforting. Whether served as a light dinner, a brunch centerpiece, or a holiday side dish, this savory tart delivers layers of flavor that feel indulgent without being heavy.

This recipe is inspired by classic European vegetable tarts, where humble ingredients are transformed through patience and technique. Caramelizing onions slowly unlocks their natural sweetness, while roasted squash adds color, body, and a mellow earthiness. Together, they create a balance that works beautifully with creamy cheese and crisp pastry.

If you’re looking for a savory squash tart recipe that’s versatile, visually stunning, and packed with seasonal flavor, this one belongs in your rotation.

Why This Caramelized Onion & Squash Tart Works

The magic of this tart lies in contrast. The onions are cooked low and slow until jammy and golden, while the squash is roasted just enough to keep its shape and subtle bite. A creamy egg-and-cream filling binds everything together without overpowering the vegetables, allowing their flavors to shine.

This rustic squash tart is also incredibly adaptable. You can use butternut squash, delicata, or even pumpkin, and the cheese can range from nutty Gruyère to tangy goat cheese depending on your preference.

Ingredients

1 prepared tart shell or pie crust
2 tablespoons olive oil
2 large yellow onions, thinly sliced
1 tablespoon unsalted butter
1 teaspoon salt
½ teaspoon black pepper
2 cups squash (butternut or delicata), thinly sliced
2 large eggs
¾ cup heavy cream
1 cup grated Gruyère or fontina cheese
1 tablespoon fresh thyme leaves
Optional: pinch of nutmeg or chili flakes

Instructions

Preheat your oven to 375°F (190°C). Place the tart shell in a 9-inch tart pan and chill in the refrigerator.
Heat olive oil and butter in a wide skillet over medium-low heat. Add sliced onions and salt. Cook slowly for 25–30 minutes, stirring occasionally, until onions are deeply caramelized and golden brown.
While onions cook, toss squash slices with olive oil and black pepper. Roast on a baking sheet for 15–20 minutes until just tender. Set aside.
In a bowl, whisk eggs and cream until smooth. Stir in grated cheese, thyme, and optional nutmeg.
Spread caramelized onions evenly over the chilled tart shell. Arrange roasted squash slices on top.
Pour the egg mixture gently over the vegetables, allowing it to settle into gaps.
Bake for 35–40 minutes, or until the filling is set and the top is lightly golden.
Let the tart cool for 10 minutes before slicing and serving.

Tips for Perfect Caramelized Onions

Use medium-low heat and be patient—rushing will burn them.
Stir occasionally, not constantly, to allow browning.
A splash of water or broth can help deglaze if onions stick.

Variations and Substitutions

Cheese Swap: Goat cheese or feta for a tangy twist.
Herbs: Rosemary or sage instead of thyme.
Crust: Puff pastry for a lighter, flakier base.
Vegan Option: Use plant-based cream and egg substitute.

Serving Suggestions

Serve this onion squash tart warm or at room temperature. It pairs beautifully with a crisp green salad, a glass of dry white wine, or as part of a holiday spread alongside roasted vegetables.

Cultural & Seasonal Context

Savory vegetable tarts have long been a staple in French countryside cooking, where seasonal produce is showcased in simple, elegant preparations. This fall vegetable tart fits perfectly into that tradition, celebrating autumn squash and slow-cooked onions at their peak.

Make-Ahead & Storage

Make up to 24 hours ahead and reheat gently.
Store leftovers refrigerated for up to 3 days.
Reheat at 325°F for best texture.