Bright green, tangy and tender, this spinach sponge cake is a delicious way to celebrate spring. The spinach, which loses its metallic edge in the oven, leaves a gentle, vegetal brightness. Baked in a shallow tin and spread with cream cheese icing, when sliced into squares, it offers the perfect ratio of cake to icing.
For the cake, you will need 120g baby leaf spinach (stems removed), 120ml milk, 200g plain flour, 1½ tsp baking powder, ¼ tsp bicarbonate of soda, ¼ tsp fine sea salt, 3 large eggs (at room temperature), 180g caster sugar, finely grated zest of 1 lime, 120ml solid coconut oil (melted and cooled to tepid), and 1 tsp vanilla extract. For the icing, you need 200g cream cheese, 100g icing sugar (sifted), finely grated zest of 1 lime plus 1 tsp juice, and 80ml double cream.
Line a 23cm x 33cm x 5cm baking tin and heat the oven to 185C (165C fan)/360F/gas 4½. Blitz the spinach and milk in a high-speed blender to a puree. Sift the flour, baking powder, baking soda and salt in a medium bowl. In an electric mixer, beat the eggs, sugar and lime zest on medium-high for three to four minutes until pale and thickened. Reduce speed to low, add the spinach puree, coconut oil and vanilla, and mix until just combined. Add the dry ingredients and mix on low until just combined.
Scrape the batter into the tin and bake for about 30 minutes, until a skewer inserted in the middle comes out clean. Cool in the tin for 30 minutes, then transfer to a rack to cool completely. For the icing, beat the cream cheese, icing sugar and lime zest with the paddle attachment on medium-high until smooth. Add the lime juice and double cream, and beat until the icing thickens and forms soft waves. Spread the icing on the cake and slice into squares to serve.
