Sieve over remaining flour, add 1 tbsp hot water and fold gently to combine. Spoon sponge equally over the rhubarb, then bake until golden and cake springs back when lightly pressed (15-20 minutes).
Gently fold this strawberry purée into the whipped cream, creating a marbled effect. To assemble the cake, carefully slice each sponge in half horizontally. Place one layer on a serving platter ...