Grease a springform pan (24 cm Ø) and dust with flour. Cream 200 g soft butter and Muscovado sugar with the whisks of the mixer. Stir in eggs one after the other. Mix 200 g flour, almonds and baking powder.
Stir into the butter-sugar cream. Smooth in the mould.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Sort blackberries and wash if necessary. Peel, quarter, core and cut apples into thin slices. Place the apple slices on the dough.
Sprinkle with berries. Press the fruit lightly into the dough. Melt 2 tablespoons of butter. Mix sugar and cinnamon. Sprinkle over the fruits and sprinkle with the liquid butter.
Bake in a hot oven for about 50 minutes (chopstick test). Let the cake cool in the tin for about 30 minutes, then carefully remove from the tin and let it cool down.