Preheat the oven to 160°C and grease a 25cm cake tin with parchment paper.
Whisk butter and sugar until pale, then gradually incorporate the eggs.
Stir in the ground almonds, polenta, baking powder, lemon zest, and lemon juice until combined.
Spoon the batter into the tin and bake for 75 minutes until golden-brown.
Mix lemon juice and sugar to create a glaze.
Prick the warm cake surface, pour over the glaze, and cool in the tin for 15 minutes.
Beat mascarpone, orange zest, orange juice, and icing sugar until smooth.
Thicken sugar and orange juice in a frying pan to create a syrup.
Cook satsuma halves in the syrup for a few minutes on each side until softened.
Serve cake wedges dusted with icing sugar alongside orange mascarpone and caramelised satsumas.