Preparation

• Preheat the oven to 180°C.
• Line a rectangular cake tin (capacity 900 g) with non-stick baking paper.
• Beat 200 g of previously softened butter with 200 g of sugar until fluffy.
• Add 3 beaten eggs, one at a time, until blended.
• Add 100 g of wholegrain flour and 100 g of plain flour, 2 teaspoons of baking powder, 100 g of bitter marmalade and 3 tablespoons of fresh orange juice.
• Pour the mixture into the baking tin and bake for 50 minutes, cover with foil for the last 15 minutes to prevent burning.
• Remove the cake from the oven and allow it to cool in the tin for 10 minutes before transferring it to a wire rack to cool completely.
• To decorate, gently heat 150 g of jam in a small saucepan with 2 tablespoons of water and spread a little on the cake.
• Peel (removing as much of the white skin as possible) and thinly slice 1 sweet orange and 1 pink grapefruit, removing the pips.
• Layer the slices on top of the sponge cake and then drizzle with the remaining jam.