Heat oven to 180C/160C fan/gas 4. Lightly butter a deep, round 20cm cake tin and line the base with a circle of non-
Place the butter in a large bowl and beat with an electric whisk until light and fluffy, then add the caster sugar and lemon zest and beat again. Gradually add the eggs to the mixture, beating well with each addition, until fully combined. The mixture will begin to look glossy – if at any stage the mixture curdles, beat in a spoonful of ground almonds and continue to add the egg until it is all amalgamated.
Stir in the ground almonds, then the flour, and fold everything carefully together using a large spoon. Fold through half the rhubarb, then transfer the mixture into the prepared cake tin and scatter with the remaining rhubarb. Finish with the demerara sugar sprinkled on top. Bake the cake for 45 mins, or until a skewer inserted into the middle comes out clean. Transfer to a wire rack to cool slightly in the tin, then remove from the tin. When the cake is cold, make the topping.
Whip the cream in a large bowl until it forms soft peaks. In a small bowl, loosen the lemon curd with about 1 tbsp water and carefully fold it through the cream, without overworking. Spread over the cake, drizzle with a little more lemon curd and serve immediately.