Put the flour with a pinch of salt in a bowl.
Add the butter or margarine and cut it into small pieces with two knives.
Stir in the quark or yogurt and quickly knead the dough by hand into a cohesive ball.
Let the dough rest in the fridge for at least 30 minutes.
Grease a springform pan with a diameter of 22 cm.
Peel and finely chop the onions.