Preheat the oven to 180°C (fan oven 160°C), gas mark 4. Line the base and sides of a 20cm (8in) springform cake tin with greaseproof paper.
Put the blood orange juice and 6 tbsp of the conserve in a large frying pan with 150ml (1/4 pint) water. Bring to the boil, stirring, until the conserve has melted.
Add the orange slices in an even layer and simmer gently for 10-15 mins or until the slices are translucent and soft. Lift the slices from the pan using a slotted spoon and use them to line the base and sides of the cake tin. Reserve the poaching liquid.
Mix together the flour, almonds, polenta and baking powder in a mixing bowl. Beat together the butter and sugar, until very pale and creamy, in a separate bowl. Gradually beat in the eggs, adding a spoonful of the dry ingredients between each addition.
Fold in the remaining dry ingredients with the orange zest, juice, vanilla essence and poppy seeds.
Spoon the cake mixture into the tin and level the surface. Bake in the preheated oven for 30 mins. Reduce the oven temperature to 170°C (fan oven 150°C), gas mark 3 and continue to bake for a further 25 mins or until a skewer inserted into the centre comes out clean.
Meanwhile, stir the remaining 2 tbsp of conserve into the reserved poaching liquid and bring to the boil. Bubble for 5-7 mins or until the liquid is reduced to a sticky syrup and set aside.
Turn the cake out onto a wire rack to cool. Brush or spoon over about half the strawberry syrup until all the orange slices are glazed.
Serve in wedges with the remaining syrup.
If using, stir the vodka into the reserved poaching liquid with the remaining conserve (step 7).
Add a generous spoonful of crème fraîche to serve.