1. Add the flour, salt, and cold butter to a large bowl and cut the butter into pea-sized pieces with a pastry cutter. Add the egg and one tablespoon of water and mix/knead everything until you get a nice smooth dough. If needed add more water. Wrap the dough in plastic wrap and place in the fridge for about 30 minutes.

 

2. Grease a 9.5 inches (24cm) round baking tin with a loose bottom. Set aside. Roll out the dough slightly larger than the tin. Place the dough inside the tin and press to the bottom and sides. Prick several times with a fork, trim the edges (it’s ok if the dough is overlapping the edges a bit) and place in the fridge for another 30 minutes.

 

3. While the dough is chilling, cut the onions into rings and fry in a pan with some olive oil until soft and lightly browned. Take out of the pan and set aside. Cut the chorizo into thin slices and fry in the same pan for some time until lightly browned. If the chorizo is very fatty, drain on a piece of kitchen paper. Set aside. Wash the zucchini and cut lengthwise into thin slices and set aside.

 

4. Preheat the oven to 390°F (200°C). Place a piece of baking parchment on top of the dough and fill the tin with baking weights. Blind bake the tart base for about 15 minutes, then remove the baking weights and bake 10-15 minutes longer until the tart base has a nice golden color. Take out of the oven and let cool down a bit.

 

5. Reduce the temperature of the oven to 350°F (180°C). Add the eggs, heavy cream, milk, and grated cheese to a large bowl and whisk to combine. Season with a good amount of salt and pepper. Place the zucchini strips rolled up on top of the tart crust, add the ricotta with a spoon into empty spaces between the zucchini, top with the onions and chorizo slices. Pour the egg-cheese mixture on top of everything and make sure it is distributed evenly. Bake for 50-55 minutes until nicely golden brown and set (cover with some aluminum foil if it gets too dark). Take out of the oven and let cool down for about 10-15 minutes, then sprinkle with some more cheese and serve.