Preheat the oven to 180C/ 160C fan/ gas 4
Line an 8" round tin with parchment paper
Beat together the butter, brown sugar, and salt for the apple layer until combined using a hand held or electric mixer
Place the mixture into the base of the tin, covering entirely
Place the apple slices on top of the butter and sugar layer, starting in the centre in a circle and following right around until the base is covered
Sieve the flour and baking powder into a large bowl
Add the caster sugar and salt and combine all ingredients
Pour in the beaten egg, milk, vanilla and melted butter and whisk until combined
Pour the sponge mixture over the apples and bake for 45 minutes
Allow the tin to cool for 5 minutes
Place a large dinner plate on top and flip the tin over to reveal the apple layer
Once cooled slightly, mix the icing powder and lemon juice to make a toothpaste consistency
Drizzle over the top of the cake to decorate
