For the cake, you will need:
225g (8oz) butter, plus some for greasing
225g (8oz) caster sugar
Finely grated zest and juice of 1 orange
110g (4oz) plain flour
1 teaspoon baking powder
Pinch of salt
110g (4oz) ground almonds
For the orange curd, you will need:
50g (2oz) butter
Zest and juice of 2 oranges
110g (4oz) granulated or caster sugar
2 egg yolks
Grease a 23cm (9in) diameter springform tin with some butter. Preheat the oven to 180°C, 350°F, Gas 4. Put the butter and the caster sugar in a bowl, then use a wooden spoon, or the paddle attachment of a stand mixer, to cream both together until they are light and fluffy.
Then beat in the eggs, one by one, along with the orange zest and the juice. Sift in the plain flour, the baking powder and the salt, then add the ground almonds and gently fold until just mixed.
Tip the mixture into the greased springform tin, then bake for 20-25 minutes, until the centre feels springy to the touch. Place on a wire rack to cool, then remove from the tin.
Put the butter in a medium saucepan on a medium-low heat. When it has melted, whisk in the orange zest, the orange juice, the granulated sugar or the caster sugar, whichever you’re using, the eggs and the egg yolks. Cook, stirring constantly, until the curd is thick enough to coat the back of a spoon. Pour over the cooled cake, then serve.