This savory tart is a labor of love that tastes just as terrific as it looks. The crust is flaky, wonderfully tender, and full of buttery goodness. The beautiful swirl at its center is made of very thin slices of fall squash, sweet potatoes, and red onions. They’re perched on a bed of Gruyère, garlic, and caramelized onions. There’s a dollop of Dijon in there, too, and it’s a brilliant, zippy foil for the roast-y veggies, melty cheese, and silky, sweet onions. The tart is very rich, and quite light, all at once.

It’s also deceptively easy to make. Sure, there are a lot of steps, but all of them are simple. Plus, fall is for red wine and long-winded cooking projects — and this one is worth every minute. On your Thanksgiving table, it will surely be the most Instagram-worthy of the side dishes. {We do love a pile of buttery mashed potatoes, but the dish has no “good side.”}

Our tip: If you want to save time, consider picking up a premade pie crust. Also, use a mandoline to slice the vegetables. It’ll get them very, very thin — and cut your prep time in half.

Servings: 6 to 8

Ingredients

For the crust:

1 cup whole wheat flour

1 tsp kosher salt

1 cup all-purpose flour, plus more for surface

10 Tbsp unsalted butter, chilled and cubed

½ cup ice water

For the pie:

4 Tbsp extra-virgin olive oil, divided

4 medium yellow onions, thinly sliced

3 cloves garlic, thinly sliced

2 Tbsp Dijon mustard

Pinch cayenne pepper

¼ cup Gruyère, coarsely grated

½ small butternut squash, halved lengthwise, sliced ⅛-inch thick crosswise

1 delicata squash, halved lengthwise, sliced ⅛-inch thick crosswise

1 small sweet potato, halved lengthwise, sliced ⅛-inch thick crosswise

1 small red onion, halved lengthwise, sliced ⅛-inch thick crosswise

Kosher salt, to taste

5 sprigs thyme

2 Tbsp unsalted butter

Flake salt, to taste

Special Equipment: 12-inch fluted tart pan with a removable bottom or 9-inch springform pan.

Directions

1. To make the crust: In a large bowl, whisk together the whole wheat flour, salt, and 1 cup of the all-purpose flour until combined.

2. Add the chilled butter and work it into the dry ingredients, pressing the butter between your fingers to flatten it, until the largest pieces are the size of a nickel.

3. Drizzle in 6 tablespoons of the ice water and rake it in with your fingers. Gently squeeze handfuls of the mixture together until a shaggy dough forms.

4. Turn the dough out onto a work surface and knead it until only a few dry spots remain. Pat the dough into a disk, wrap it in plastic and chill until very firm, at least 2 hours or up to 3 days.

5. Using a rolling pin, roll the dough out on a lightly floured surface to about ⅛-inch thick.

6. Transfer the dough to a 12-inch fluted tart pan. Lift up the edges and allow the dough to slump down into the pan. Gently press the dough into the corners and trim the excess. (If using a springform pan, trim the dough to 1 ½ inches up the sides of the pan.)

7. Place the tart pan in the freezer for 15 to 20 minutes, or cover and chill for up to 12 hours.

8. To make the filling and assemble the pie: Preheat the oven to 350° and place an oven rack in the lower third of the oven.

9. In a large skillet, heat 2 tablespoons of the olive oil, add the onions and cook, stirring occasionally, over medium heat until the onions are soft and golden brown, 15 to 20 minutes.

10. Add the garlic and cook, stirring occasionally, until the onions are caramelized, 25 to 30 minutes. Let the onions cool.

11. Brush the Dijon mustard over the chilled dough, and then sprinkle it with cayenne pepper.

12. Stir the cheese into the caramelized onion mixture and spread the mixture across the crust in an even layer.

13. Arrange the vegetables in concentric circles, starting from the outside edge and working your way inward, with the round edges standing up and the slices leaning against the crust — you’re creating a kind of rose, so you don’t want the slices to lay flat.

14. Drizzle the remaining 2 tablespoons of olive oil over the vegetables and season with kosher salt.

15. Bake the tart until the edges of the vegetables are browned and the crust is golden brown, 75 to 90 minutes.

16. In a small saucepan, combine the thyme and unsalted butter and cook just until the butter is bubbling.

17. Brush the butter mixture over the tart with a pastry brush, sprinkle with flake salt, and serve warm or at room temperature.

Recipe source: Bon Appétit

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