Ingredients

• 2 cup all-purpose flour
• 8 ounce unsalted butter, cold, cubed
• 1 teaspoon sea salt
• 1 tablespoon fresh thyme, chopped
• 1 egg yolk
• 4.5 tablespoon ice water, ice cold
• 3 tablespoon olive oil
• 2 yellow onion, thinly sliced
• 1 eggplant, diced into ½-inch cubes
• 2 zucchini, cut into ¼-inch rounds
• 1 red bell pepper, diced
• 4 garlic, minced
• 0.5 teaspoon black pepper
• 1 teaspoon dried oregano
• 0.5 cup Gruyère cheese, shredded
• 2 tablespoon fresh basil, chopped

Steps

1. In a food processor, combine the flour, sea salt, and chopped fresh thyme. Pulse to combine.
2. Add the cold butter cubes to the food processor and pulse until the mixture resembles coarse breadcrumbs with some pea-sized butter pieces remaining.
3. In a small bowl, whisk together the egg yolk and 4 tablespoons of ice water.
4. Add the egg mixture to the flour mixture in the food processor and pulse just until the dough comes together. Add the remaining tablespoon of ice water if needed.
5. Form the dough into a disk, wrap in plastic wrap, and refrigerate for at least 20 minutes while you prepare the vegetables.
6. Heat 1½ tablespoons of olive oil in a large skillet over medium heat. Add the sliced onions and cook for 15-18 minutes, stirring occasionally, until deeply caramelized and golden brown.
7. While the onions cook, prepare the eggplant: dice it into ½-inch cubes and place in a colander. Sprinkle with ½ teaspoon of salt and let sit for 5 minutes to draw out excess moisture, then pat dry with paper towels.
8. Cut the zucchini into ¼-inch rounds and dice the red bell pepper.
9. Preheat the oven to 400°F (200°C).
10. When the onions are caramelized, stir in the minced garlic and cook for 1 minute until fragrant. Remove from heat.
11. On a floured surface, roll out the chilled pastry dough into a 13-inch round approximately ¼-inch thick. Transfer to a parchment-lined baking sheet.
12. Spread the caramelized onion mixture evenly over the pastry, leaving a 1½-inch border around the edge.
13. Fold the pastry border up and over the filling, pleating it loosely as you go (it should cover about 2 inches of the filling at the edges).
14. In a bowl, toss the eggplant cubes, zucchini rounds, and diced red bell pepper with the remaining 1½ tablespoons of olive oil, the remaining ½ teaspoon of sea salt, black pepper, and dried oregano.
15. Arrange the vegetable mixture on top of the caramelized onions in overlapping layers or rows, working in a decorative pattern if desired.
16. Sprinkle the shredded Gruyère cheese evenly over the vegetables.
17. Bake for 35-40 minutes until the pastry crust is golden brown and the vegetables are tender and lightly browned at the edges.
18. Remove the tart from the oven and let cool for 5 minutes. Garnish with fresh basil and additional fresh thyme before serving.