Grease the glasses and sprinkle with the breadcrumbs. Preheat oven to 175 degrees.
Beat the butter until foamy, spoon in the sugar mixed with vanilla sugar, lemon zest and salt. Beat in the eggs one by one (each egg about 1/2 minute). Finally stir in the quark. Mix the flour with the baking powder and fold in. Stir in the mineral water.
Pour the batter into the jars, place on the oven rack and bake for 50 minutes.
Close immediately after baking.
For immediate consumption, mix powdered sugar with lemon juice and decorate the cakes with it.