100 g / 3 ½ oz butter, softened
¾ dl / 3 ½ tbsp. white or brown sugar
1 small egg
2 ½ dl / 1 cup wheat flour
½ tsp. baking powder
Cream the butter and sugar together. Beat in the egg until smooth. Mix in the flour and baking powder. Line a springform pan (approx. 24 cm) with parchment paper. Pat the mixture in the bottom and up the sides of the pan. Set aside in a cool place while you make the filling.
For the filling:
250 g / 8.8 oz quark (farmer’s cheese)
200 g / 7 oz plain cream cheese
2 tsp. lemon juice
1 tbsp. potato starch
2 tsp. vanilla sugar
2 eggs, separated
2 dl / 1 cup granulated sugar
2 dl / 1 cup whole lingonberries
Mix the quark, cream cheese, lemon juice, potato starch, vanilla sugar, egg yolks and half the granulated sugar in a bowl until smooth.
In another bowl, beat the egg whites until soft peaks form. Gradually fold in the rest of the sugar. Beat until stiff peaks form and the whites are glossy. The whites should be stiff enough to not fall out of the bowl, even if you turn it upside-down.
Fold the cheese mixture and the lingonberries into the egg whites. Pour into the springform pan.
Bake in a 175 °C/350 °F oven on the lowest rack. After 30 minutes, cover with a piece of parchment paper, so the top does not get too dark. Continue baking for about 20 minutes or until the cake is cooked through. Let cool.