1. Combine flour and salt in a large bowl, add the cold butter in small pieces, and cut into even smaller pieces with a pastry cutter*. Mix the egg and one tablespoon of the milk, add to the bowl and stir in. Mix/knead until the dough starts holding together – if not, add a bit more milk. Shape into a ball, flatten it, and wrap in plastic wrap. Place in the fridge for at least 1 hour.

2. Lightly grease an 11-inch tart tin with a loose bottom*. Roll out the dough on a lightly floured surface slightly larger than the tart tin, transfer to the tin, and press to the bottom and sides. Trim off overlapping dough. Prick the bottom of the tart several times. Place in the fridge until needed.

3. For the filling, mix the sour cream with the eggs and Parmesan in a bowl. Remove the small thyme leaves from the stalks, add to the bowl, and season well with salt and pepper. Set aside.

4. Wash and dry the veggies and cut them into thin slices. Peel and thinly slice the onions as well. Heat some oil in a large frying pan and sauté the veggie slices briefly. The eggplant slices will take the longest to get some color. The zucchini will brown fairly quickly and the tomato slices really only need to be sautéed for a few seconds on one side – otherwise, they will fall apart. Place the sautéed veggie slices on plates or a small tray. Be careful with the tomatoes. Season with some salt and pepper and let cool a bit.

5. Preheat the oven to 350°F (180°C) top/bottom heat. Remove the tart base from the fridge, spread the sour cream mixture on the bottom, and then start layering the veggie and onion slices on top. Start on the outside and place the slices alternating in a circle on top of the filling – always slightly overlapping the previous slice. When done, season with some more salt and pepper (if you like) and bake the tart in the preheated oven for about 55-60 minutes. I recommend baking in the lower third at the beginning, so the base bakes properly. Later you can place the tart closer to the upper heating element – this way the veggies can also brown a little. Remove the tart from the oven, let it cool a bit on a cooling rack, then carefully remove from the baking tin. Place on a serving plate and serve warm with your favorite (sour cream) dip/sauce.