Preheat the oven to 200 C / 180 C fan / Gas 6. Line a 12 hole muffin tin with paper cases.
Add the butter to a bowl and cream with the sugar. Then sieve in the flour and mix in thoroughly.
Whisk the eggs together in a separate bowl. Add the eggs to the cake mixture and beat until smooth. Add the apple and vanilla to the mix. Spoon into the prepared paper cases, filling no more than 2/3 full to ensure a good rise.
Bake in the preheated oven for 12 to 15 minutes until risen and golden and a skewer inserted into the centre comes out clean. Remove from the oven and allow to cool completely.
While the cakes are cooking grab another bowl and add in around 2 tablespoons of icing sugar. Mix in 1 of the 2 teaspoons of water. If the icing sugar gets too runny add more icing sugar; too thick, add more water.
Once the cakes are cool drizzle the icing sugar over the top and add 1 raspberry on the top. Enjoy!