Let the butter melt. Meanwhile, whisk the eggs with the sugar until foamy.
Then stir in the melted butter and add the flour with the baking powder and salt. Mix everything well and fill into the muffin cups. Peel and core the apple and cut into small cubes. Spread the apple cubes and a few raisins on the muffins.
Finally, put 1 teaspoon of sugar-cinnamon mixture on each of the muffins. Then put the whole thing in the oven at 175°C for 25 – 30 minutes. When the muffins have cooled down, I dust them with powdered sugar.
