Preheat the oven to 180°C fan/200°C/gas 6, and line and butter a 30 x 37cm roasting or baking tin with non-stick or greaseproof paper. Slice the apples and dress them with a little lemon juice to stop them going brown.

Beat the butter and sugar together until smooth, then whisk in the eggs, one by one. Gently stir in the flour, baking powder and spices until just combined.

Transfer the cake batter into the lined tin, and top with the sliced apples in a design of your choice. I like to make them slightly overlapping.

Beat the demerara sugar and butter together, then stir in the flour and oats and work with your fingertips into a rough crumble. Scatter this over the cake, then transfer to the oven and bake for 30 minutes, until the topping is golden brown and a skewer inserted into the cake comes out clean.

Let the cake cool in the tin for 5 minutes before lifting it out with its paper on to a wire rack to cool down. Serve warm with crème fraîche, or at room temperature.