Grease the cavities of a ring cake baking tray (6 cavities; each containing approx. 200 ml) and dust with flour. Preheat the oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer).
For the dough, rinse lemon hot, dab dry and finely grate half of the peel. Halve the lemon. Squeeze half and measure 3 tbsp. Cream 200 g butter, sugar, 1 pinch of salt and the lemon zest with the whisk of the mixer.
Stir in the eggs one by one. Mix 225 g flour, starch and baking powder. Stir milk into the egg-sugar mixture and finally stir in 1 tbsp. lemon juice.
Spread the dough into the hollows. Bake in a hot oven for 25-30 minutes. Remove from the oven and let cool for about 5 minutes. Carefully turn the balls out of the tin and let them cool down.
For the icing, stir icing sugar, 4 tablespoons water and 2 tablespoons lemon juice until smooth. Coat the ring cake with the icing, leaving out the middle recess. Leave to dry for about 1 hour.
Stir mascarpone and vanilla sugar until smooth. Stir in cherry jam. Pour into the ball wells just before serving.