Grease a spring form round tin (23cm), line the bottom and sides with baking paper and grease again.

In a small saucepan over medium heat, melt 45 g butter. Then add the brown sugar and lemon juice, cardamom pods and rosemary sprig. Stir until the sugar melts, about 3 minutes. Remove the aromatics with a spoon and then scrape the syrup into the bottom of the prepared tin

Grate the zest from orange and reserve for the cake batter. Then slice off the tops and bottoms of both oranges. Remove the rind and pith, following the curve of the fruit from top to bottom. Then cut the oranges into 0.5 mm wheels. Arrange the wheels on top of brown sugar mixture in a single, tight layer.

Beat the butter and sugar in a large bowl until light and creamy. Beat in the eggs one after the after, and stir in the vanilla extract.

In a second bowl combine the ground almonds, polenta, orange zest, orange blossom water and baking powder. Stir this into the cake mix.

Pour the batter over the syrup and blood oranges and bake for 40 -50 minutes, until the top is light brown and cake is slightly loose from the sides of the tin.

Allow to cool for 10 minutes. Remove from the tin and carefully turn out onto a plate. Delicately remove the greaseproof from the cake. Serve with crème fraiche, and a grating of orange peel.