Blueberry lemon cake with coconut crumble topping

Heat oven to 180C/fan 160/gas 4 and grease and line a 20 x 30 cm cake tin with baking parchment. Beat together 250g of the butter with 250g sugar and the lemon zest until light and fluffy. In a separate bowl, break up 4 eggs with a fork, then gradually beat into the butter and sugar mixture, adding a spoonful of flour if it begins to curdle. When the eggs are incorporated, fold in the flour and a third of the blueberries, then spoon into the tin. Flatten the surface with a spatula, sprinkle over another third of the blueberries, and bake for 20 mins until the surface is set.

To make the topping, melt the rest of the butter, then stir in the coconut and remaining sugar and eggs until combined. Warm the lemon curd gently for a few mins in a small pan until it is runny and pourable.

After the initial baking, scatter the remaining blueberries over the top of the cake, drizzle over the lemon curd, and crumble over the coconut mixture. Bake for a further 20-25 mins until the coconut is golden. Leave the cake in the tin to cool. Cut into 16 squares and store in a tin, interlined with greaseproof paper.