Beat the fat, 150 g sugar, vanillin sugar and salt with the whisk of the hand mixer until foamy. Stir in the eggs one after the other. Wash 1 lemon, dab dry and grate the peel. Halve the lemon and squeeze the juice. Stir the peel and juice into the fatty egg mixture.
Mix flour and baking powder. Alternately stir briefly with the milk. Line the troughs (12 pieces) of a muffin tin with paper cups. Fill each well to 3/4 with dough. Bake in the preheated oven (electric: 175 °C/ convection oven: 150 °C/ gas: level 2) for 25-30 minutes. Let muffins cool down for about 1 hour.
Meanwhile wash the lemon, rub dry and halve it. Cut one half into different slices and roll in 20 g sugar. Squeeze the other half. Mix icing sugar with lemon juice to a thin icing and cover the muffins with it. Decorate with lemon wedges.