Pour the orange juice into a jug and add enough cold water to make 250 ml liquid.
Add the apricots to a pan, pour in the juice. Bring to the boil, then cook for 10 minutes until the apricots become soft. Cool, then blend it into a smooth purée.
With an electric whisk beat the butter, sugar and orange zest. Add the eggs one-by-one, whisk gently.
Stir in the purée, then gently fold in the ground almonds, polenta and baking powder.
Grease and line the base of a cake tin (about 22 cm).
Tip the batter into the tin and even out the surface.
Bake for about 45 minutes in a preheated oven at 180°C.
Insert a skewer into the middle, if it comes out clean, the cake is cooked through. If not, bake it for another 5-10 more minutes. Do the skewer test again.
Leave the baked cake in the tin to cool for about 10 minutes then turn it onto a wire rack.
Let it cool completely before serving.