HEALTHY SPONGE CAKE WITH CUSTARD

Separate the egg whites from the yolks and whip until stiff peaks form.

Add the kefir, sweetener, flour, and baking powder to the yolks, and mix thoroughly.

Gently fold in the egg whites using a spatula, moving from the bottom up.

Pour the batter into a 12 cm cake pan and bake in a preheated oven at 180°C for 20 minutes.

Let the finished sponge cake cool, then cut it into 2 layers.

Add the cornstarch, egg yolk, and sweetener to the milk, mix well, and place over low heat.

Cook, stirring constantly, until thickened.

Let the custard cool slightly, then add the quark. Whip the cream with a whisk.

Assemble the cake by spreading the cream between the layers.