Separate the eggs. Mix the butter, sugar and ricotta until foamy, stir in the egg yolks one at a time. Mix the flour and baking powder and stir in as well. Add the grated lemon zest and juice.
Beat the egg white until stiff and fold it carefully into the ricotta mixture. Place the cake in a greased and sprinkled Guglhupf tin and bake for about 45 minutes at 180 ° top and bottom heat.
After cooling, remove the cake from the mold and sprinkle with powdered sugar.
A scoop of lemon ice cream and a dollop of whipped cream tastes great with it.