Preheat the oven to 180C/355F/Gas 4.
Beat the butter and sugar together in a bowl until pale and fluffy.
Add the almonds and mix together well.
Add the eggs, one at a time, beating to combine well before adding the next egg.
Add the vanilla essence and the fruit juices and zests and mix well.
Add the polenta, salt and baking powder and stir well to combine.
Spoon the cake mixture into a 30cm/12in greased and floured cake tin and transfer to the oven to bake for 45-55 minutes, or until golden and firm. If the top begins to brown too soon, cover with baking paper to protect the top from burning while the rest of the cake cooks. Remove from the oven and allow to cool.
For the sauce, place the butter and sugar into a pan over high heat and cook until they melt and begin to caramelise.
Add the orange blossom water and orange juice and stir well. Simmer for four minutes, until combined.
To serve, slice a piece of cake and place onto a plate. Add a dollop of mascarpone and drizzle the sauce around.