For the crumble dough, wash the lemon hot, dab dry and finely grate the peel. Put the flour, 175 g brown sugar and 350 g butter in pieces in a bowl. First knead into crumbles with the dough hooks of the mixer, then with your hands.
Cut a fat pan (approx. 32 x 39 cm; deep baking tray) in half using a thick strip of aluminium foil. Grease one half of the baking tray. Approx. 2⁄3 Press the crumbles onto it to form a base. Chill with the rest of the crumble dough for about 30 minutes.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Let the blueberries thaw for approx. 10 minutes. Separate eggs. Beat the egg whites until stiff, adding 75 g sugar. Mix egg yolk, quark, milk, 100 g sugar and pudding powder with the whisks of the mixer until creamy.
Fold in the beaten egg white. Pour onto the crumble base. Sprinkle with berries.
Bake in a hot oven for 45-55 minutes. Mix the rest of the crumble, grated coconut and 2 tablespoons of brown sugar. After about 15 minutes baking time, spread the coconut crumbles on the cake (note: the cheese mixture is still relatively soft) and continue baking.
Remove and let it cool down.