Citrus and honey cake

For the cake:

For the cake:

175g (6oz) unsalted butter, softened, plus more for the tin

plain flour, for the tin

1 orange, washed

1 thin-skinned waxed lemon, washed

25g (1oz) roasted hazelnuts, plus 12 whole hazelnuts to decorate (optional)

110g (4oz) almonds

175g (6oz) Demerara sugar

3 large free-range eggs

250g (9oz) semolina

1 tsp baking powder

For the sauce:

225ml (8fl oz) runny honey, ideally orange blossom honey

4cm (1 ½ inch) cinnamon stick

juice of 1 orange

juice of ½ lemon

Creme fraiche, or a mixture of whipped cream with yoghurt, to serve (optional)