Wash and sort blueberries. Melt butter in a pot. Whisk eggs and condensed milk with the whisk of the hand mixer until creamy. Mix flour and baking powder and stir in. Stir in butter
Put blueberries into a greased and flour-spread springform pan (approx. 20 cm Ø) and spread dough on top. Bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for 35-40 minutes. If necessary, cover with foil about 10 minutes before the end of the baking time. Take out, let cool down a little and turn out of the tin