We love the color and texture you get from using a combination, but any single root vegetable can be used here, too.
1 medium Yukon Gold potato, peeled, sliced into ½” rounds
1 medium sweet potato, peeled, sliced into ½” rounds
2 medium carrots, peeled, sliced into ½” rounds
1 medium parsnip, peeled, sliced into ½” rounds
1 small red onion, sliced into ½” rounds
¼ cup olive oil
Kosher salt and freshly ground black pepper
⅓ cup sugar
1 tablespoon white wine vinegar
1½ teaspoons chopped fresh rosemary
1½ teaspoons chopped fresh sage
4 ounces fresh goat cheese
1 disk All-Butter Pie Dough (click here for recipe)
All-purpose flour (for surface)
Place a rack in lower third of oven; preheat to 400°. Toss potato, sweet potato, carrots, parsnip, and onion with oil on a rimmed baking sheet; season with salt and pepper and arrange vegetables in a single layer. Roast until golden around the edges and tender, 30–35 minutes. Let cool.
Meanwhile, cook sugar and 2 Tbsp. water in a small saucepan over medium-high heat, swirling pan occasionally, until mixture is amber-colored, 5–7 minutes. Remove from heat and add vinegar and a pinch of salt, swirling pan to combine. Quickly pour caramel into a 9”-diameter pie pan; tilt and rotate pan to evenly coat bottom with caramel. Scatter rosemary and sage over top.
Arrange potatoes, carrots, and parsnips snugly in a single layer on top of caramel, using smaller carrot and parsnip pieces to fill in any holes. Scatter onion rings and crumble goat cheese over vegetables.
Roll out dough on a lightly floured surface to a 12” round. Drape over vegetables, tucking edges into pan. Prick dough all over with a fork. Bake until crust looks dry, about 20 minutes; reduce heat to 350° and bake until crust is golden brown, 15–20 minutes.
Let tart cool 5 minutes before inverting carefully onto a large plate.
DO AHEAD: Vegetables can be roasted 4 hours ahead. Keep at room temperature.