Method

1. Preheat the oven to 180C/350F/Gas4, and grease and line a 23cm/9in springform cake tin.

2. Mix the custard and half of the raspberries in a bowl until well combined.

3. In a separate bowl, beat the butter and sugar together until creamy, then add the eggs, one at a time, until well combined.

4. Stir in the flour, baking powder, milk, and the remaining crushed raspberries.

5. Pour half the cake mix into the cake tin. Add the raspberry custard mixture, and top with the remaining cake mixture.

6. Sprinkle with the demerera sugar and bake in the oven for 1½ hours. (Test the cake by inserting a skewer into the centre. If the skewer comes out clean, the cake is done.)

7. Remove the cake from the oven and set aside to cool. Remove from the tin and cut into slices.