Preheat the oven to 180°C.
Grease and line two 23cm spring-form cake tins with parchment.
Cream the butter and sugar for five minutes until light and white.
Beat in the eggs one at a time until fully incorporated.
Stir in the vanilla extract and fold in the flour.
Distribute the batter into tins and bake for 25-30 minutes.
Check with a skewer and cool the cakes on a wire rack.
Combine 250g icing sugar, 125g butter, and hot water for the buttercream.
Mix the cinnamon into the buttercream until smooth.
Level the top of one sponge layer.
Spread the jam and then the buttercream over the levelled cake.
Place the second sponge on top and press down gently.
Dust the top with extra icing sugar and slice to serve.