Sift the flour and baking powder. Melt the butter (warm it until liquid, but not hot) and mix with the sugar, salt and lemon zest. Fold in the yoghurt, eggs and flour mixture.
Halve the raspberries. Briefly roll a rolling pin over the granola, if the clumps are too big. Lightly / quickly fold the raspberries and the granola into the mixture and then transfer it to the cake pan.
Bake for 12 to 15 minutes at 375°F. When done, leave the cakes to cool and sprinkle with powdered sugar.