This is a perfect cake to make as a special occasion cake – an ideal birthday cake for a lover of all things lemon. Just an inside tip – it is my favourite choice for my own birthday…just in case you needed to know 😉
Makes one 8-inch (20 cm) cake.
Lemon Coconut Filling
Sabayon Buttercream & Assembly
Preheat the oven to 350ºF (180ºC). Grease two 8-inch (20 cm) round cake pans. Line the bottoms with parchment paper and dust the sides of the pans with flour, tapping out any excess.
Sift the flour, sugar, baking powder and salt into a large mixing bowl (if using electric beaters) or into the bowl of a stand mixer fitted with the paddle attachment. Add the lemon zest and stir in. Add the butter and cut in on medium-low speed until the flour is crumbly and no pieces of butter are visible, about 2 minutes.
In a separate bowl, whisk the buttermilk, lemon juice, oil, eggs and vanilla. Add this all at once to the flour and mix first on low speed until combined and then increase the speed to medium high and beat for 1 minute until lighter in colour. Divide the batter between the two pans and spread to level. Bake the cakes for about 30 minutes, until a tester inserted in the entre of a cake comes out clean. Cool the cakes for 30 minutes on a rack in their tins, then turn out to cool completely.
For the filling, measure the cream, sugar, lemon zest, cornstarch and coconut in a saucepan and whisk this together. Have the egg yolks in a small dish and have the butter in another dish on hand. Bring the cream mixture up to a full simmer over medium heat while whisking, about 5 minutes. Ladle a spoonful of the cream into the egg yolks while whisking and then add this back into the pot, and continue to cook for about 4 minutes while whisking, to cook the eggs. Remove the pan from the heat and whisk in the butter until melted. Whisk in the vanilla and coconut extract (if using) and transfer to a bowl to cool. Cover and chill for at least 4 hours before using.
For the buttercream, whisk the egg yolks, sugar, lemon zest and juice in a metal bowl placed over a pot of gently simmering water, until the mixture has doubled in volume and holds a ribbon on the surface when the whisk is lifted. Remove the bowl from the heat and whisk in the icing sugar – this will cool the sabayon. Using electric beaters or in a stand mixer fitted with the whip attachment, whip the sabayon one minute to cool it further and then add the soft butter a few pieces at a time, until the buttercream is smooth. Whip in the vanilla. Use the buttercream at room temperature.
To assemble the cake, slice each cake layer in half horizontally. Place one cake layer onto a platter or cake stand. Spoon some of the buttercream into a piping bag fitted with a large plain tip and pipe a ring around the outside edge of the cake. Spoon a third of the chilled coconut filling inside this ring, spreading evenly. Top this with another cake layer and repeat two more times. Cover the top and sides of the cake with the remaining buttercream and coat the entire cake with coconut. Chill the cake until ready to serve.
The cake should be stored refrigerated, but it best enjoyed when it sits out an hour before slicing and serving.