Squash Tart | Recipe Cart | Recipe Cart

Ingredients

• 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
• 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