Step 1

Preheat oven to 180C or 160C fan. Grease a 20 cm springform tin, and line base with non-stick baking paper. Use electric beaters to beat butter and caster sugar until light and creamy. Add egg and beat until combined, then beat in the vanilla.

Step 2

Sift flour and cinnamon over butter mixture, and add milk. Use a rubber spatula to fold together until just combined; don't overbeat. Spread cake batter in prepared tin, and smooth the surface.

Step 3

Quarter and core apples, then cut into thin slices. Arrange apple on the batter. Bake for 35-40 mins, or until golden brown and firm to a gentle touch in the centre. Brush warm cake with melted butter, and sprinkle with demerara sugar.