Melt the butter. Mix flour, polenta, baking powder, 1 pinch of salt and 65 g sugar. Mix butter, buttermilk and egg with the whisk of the hand mixer into the dry ingredients. Fill the dough into a greased square springform pan (24 x 24 cm).
Clean, wash and halve the plums, remove the core and cut into slices.
Spread the plums on the dough like roof tiles. Sprinkle almonds over it and bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for approx. 15 minutes. Remove the cake from the tin and let it cool down on a cake rack.
Whisk the egg white with the whisk of the hand mixer until stiff, adding 100 g sugar. Spread plum puree inside in strips on the edge of a piping bag with perforated spout (approx. 1 cm Ø).
Carefully pour the beaten egg white into the piping bag and spray tuffs onto the cake. Carefully flame off with a Créme Brúlee burner. Cut the cake into pieces and serve.