This is one of those cakes that gets better with time – if you are making this to give as a birthday cake I recommend making it at least 24 hours in advance, for ultimate orangey flavour and incredible moisture.

Ingredients

For the curd

1 egg + 1 yolk

110g sugar

1 large orange

Lemon juice, tablespoon

Unsalted butter – 55g

For the cake:

Margarine – 175g

Caster sugar – 175g

Self-raising flour – 175g

Baking powder – 1 teaspoon

Orange, 1, zest and juice

For the buttercream

Icing sugar, 400g, sieved

Unsalted butter, room temperature, 100g

Juice of 1/2 orange

Vanilla extract

Method

To make the orange curd filling, in a small heatproof bowl beat the egg and extra yolk together. Add in the sugar, orange zest and juice, the lemon and the butter. Mix until roughly combined (the butter will still be chunky). Place the bowl over a pan of simmering water, without the bowl touching the water, and stir attentively as the mixture melts together and eventually turns thick. This should take around 15 minutes but could take a little more. When thick, pour into a clean empty jam jar and leave to cool. Store in fridge until ready for use (it will keep for up to three weeks!).

For the cake, add all ingredients into a large bowl and whisk on a medium speed with a hand whisk until well combined and airy – a couple of minutes. Pour into two 19cm round cake tins greased and lined with greaseproof paper. Bake for around 20 minutes or until the cake is coming away from the sides of the tin and springs back to the touch in the centre. Turn out to cool on a wire rack.

Once cake is cool, make the buttercream for the outside. Whip the butter in a bowl to get it really soft. Add a small amount of icing sugar and a drop of orange juice and vanilla extract. Mix very well to remove lumps. Continue to add the icing sugar, mixing well, and add in more orange juice as needed to achieve a fairly thick but easily spreadable consistency – too thick and you will rip the cake surface when you spread it on.

Assemble the cake by spreading  a generous layer of the curd on both pieces of the sponge. Gently sandwich together and scrape off any excess curd that spills out of the sides. Now cover the whole cake with the buttercream. I prefer to do this very thinly otherwise it becomes too sickly. Decorate to your preference – I use dehydrated orange slices (thinly slice an orange, arrange the slices on a baking tray covered with greaseproof paper and leave in the oven at 90ºC for about 2.5 – 3 hours).