Combine soft butter with sugar and lemon zest, add the eggs and stir until creamy, then stir in the flour and starch mixed with baking powder with the yoghurt, finally stir in the pieces of fruit and raisins with a spoon, pour the dough into a prepared baking tin and place in the preheated oven Bake at 160 ° hot air for about 45 minutes (stick test).