Start by making the dough. Cut the butter into cubes, quickly to avoid melting. Transfer to a big bowl and add the flour. Use a pastry cutter, two forks or even your fingertips to cut in the butter cubes. Cut in the butter until the mixture resembles coarse meal. You should have some larger pieces of butter when you’re done.
Add the egg and work the dough. It should come together easily and should not feel overly sticky. Wrap each tightly in plastic wrap and refrigerate for at least 1 hour or up to 5 days.
Preheat the oven at 220 ºC.
Slice the eggplant in 1cm thick. If too big, cut in half. Transfer to a bowl with water and 1 tablespoon of salt. Set aside.
Prepare the other veggies: slice the zucchini in 1cm thick, halve the tomatoes, slice finely the leeks, cut the bell pepper into cubes (remove the seeds and white parts), cut the onions into quarters, peel the garlic cloves.
Remove the eggplant from water and place into a baking tray. Add 3 tablespoons of olive oil and roast for 15 minutes.
Add the other ingredients to the baking tray, season with salt and pepper, and mix gently. Roast for more than 30 minutes. Remove from the oven.
Turn the oven to 180 ºC.
Remove the dough from the fridge. Open it on a clean countertop with flour to 0.5cm thick.
Place the dough into a 24 cm springform tin or place parchment paper to a normal baking tray of the same size. The dough needs to be larger than the tray.
Roasted veggies over the dough and add the thyme and rosemary. Mix gently.
In a bowl mix the egg yolk and water, brush the dough with the mixture and take the tart to the oven to bake for around 45 minutes until golden. Serve hot or ambient temperature.