Squash and Caramelized Onion Tart
Squash and caramelized onion tart
A beautiful vegetarian main meal for your Arteflame Pizza Oven!
- 1 cup whole wheat flour
- 1 tsp. kosher salt
- 1 cup all-purpose flour, plus more for surface
- 10 Tbsp. chilled unsalted butter, cut into pieces
- FILLING AND ASSEMBLY
- 4 Tbsp. extra-virgin olive oil, divided
- 4 medium yellow onions, thinly sliced
- Kosher salt
- 3 garlic cloves, thinly sliced
- 2 Tbsp. Dijon mustard
- Pinch of cayenne pepper
- 4 oz. coarsely grated sharp cheddar or Gruyère
- ½ small butternut squash (a lengthwise half, about 1¼ lb.), seeds removed
- 1 delicata squash (about 1 lb.), halved lengthwise, seeds removed
- 1 small sweet potato
- 1 small red onion
- 2 sprigs thyme
- 2 Tbsp. unsalted butter
- Flaky sea salt
An 11"- or 12"-diameter fluted tart pan with removable bottom or a 9"-diameter springform pan
Whisk whole wheat flour, salt, and 1 cup all-purpose flour in a large bowl to combine. Add butter and work into dry ingredients with your fingers, smashing between your palms to flatten, until largest pieces are the size of a nickel. Drizzle in 6 Tbsp. ice water and rake in with your fingers. Gently squeeze handfuls of mixture together until a shaggy dough forms. Turn out onto a work surface and knead until only a few dry spots remain. Pat into a disk and wrap in plastic. Chill until very firm, at least 2 hours or up to 3 days.
Roll out dough on a lightly floured surface to about ⅛" thick. Transfer to tart pan. Lift up edges and allow dough to slump down into pan. Gently press into corners and trim excess. (If using springform pan, trim dough to 1½" up sides of pan). Freeze until firm, 15–20 minutes, or cover and chill up to 12 hours.
FILLING AND ASSEMBLY
Heat up the Arteflame Grill and attach your Pizza Oven Grate attachment. Meanwhile on the side plancha, pour oil to coat surface and add yellow onions; season with kosher salt. Cook onions, stirring occasionally until very soft and deep golden brown, 15–20 minutes. Add garlic and cook, stirring occasionally, until onions are caramelized and deeply browned, 25–30 minutes. Let cool.
Brush mustard over chilled dough, then sprinkle with cayenne. Stir cheese into caramelized onion mixture and spread across crust in an even layer.
Using a mandoline or very sharp knife, thinly slice both squashes crosswise. Cut sweet potato and red onion in half lengthwise, then thinly slice crosswise with mandoline. Arrange vegetables in concentric circles, with rounded edges facing up, starting from the outside edge, leaning slices against the crust, and working your way inward. Drizzle remaining 2 Tbsp. oil over vegetables and season with kosher salt.
Bake tart under the Pizza Oven until edges of vegetables are browned (a few spots may even get deeply browned) and crust is golden brown, approximately 30-60 minutes.
Melt thyme and butter in a small saucepan and cook just until butter is bubbling. Brush over tart with a pastry brush and sprinkle with sea salt.