Heat oven to 180C/160C fan/gas 4. For the topping, beat the butter and sugar together until creamy. Spread over the base and a quarter of the way up the sides of a 20-21cm round cake tin. Arrange pineapple rings on top, then place cherries in the centres of the rings.
Place the cake ingredients in a bowl along with 2 tbsp of the pineapple syrup and, using an electric whisk, beat to a soft consistency. Spoon into the tin on top of the pineapple and smooth it out so it’s level. Bake for 35 mins. Leave to stand for 5 mins, then turn out onto a plate. Serve warm with a scoop of ice cream.