Rhubarb upside-down cake
- Preheat oven to 180C. Place the egg whites, ground almonds, icing sugar, flour and butter in a bowl and mix well to combine.
- Lightly grease the base of a 20cm square cake tin and sprinkle with the caster sugar. Arrange the rhubarb pieces in the base of the tin.
- Pour over the cake mixture and bake for 40-45 minutes or until springy to touch. Gently invert the cake to remove from the tin. Cool on a wire rack.