Mix all the ingredients for the tart crust well with a spoon and turn the dough out onto a floured surface, where it is kneaded until smooth and elastic.
Roll out the crust into a circle and place it in a greased tart pan.
Pre-bake at 200 degrees Celsius (392 degrees Fahrenheit), conventional oven, for 10 minutes.
Meanwhile, finely chop the spinach, halve the tomatoes, and cut chorizo + potatoes into cubes.
Distribute the spinach, chorizo, and potatoes in the pre-baked crust and sprinkle grated cheese on top.
Whisk together the ingredients for the egg mixture and pour it into the tart so it is evenly distributed.
Bake the tart for another 40 minutes or so, until it is golden and the egg mixture is set.