Polenta Cake with Orange Sauce

Preheat the oven to 350 degrees F (175 degrees C). Grease a 9-inch springform pan and dust with flour.

Combine butter and sugar in a bowl and beat with an electric mixer until light and creamy. Beat eggs in a separate bowl until light and foamy and mix into the butter-sugar mixture.

Sift flour, polenta, and baking powder together. Fold into the batter. Stir in rum, lemon juice, orange juice, lemon zest, and orange zest. Pour batter into the prepared springform pan and level with a spatula.

Bake in the preheated oven until a toothpick inserted into the center comes out clean, 50 to 60 minutes. Cover top with aluminum foil if it starts browning too quickly.

Cool on a wire rack for 5 minutes. Run a table knife around the edges to loosen. Remove carefully onto a serving plate or cooling rack. Let cool completely.

Stir orange juice and orange marmalade together in a saucepan. Heat over low heat until it has reduced to a thick sauce, 5 to 10 minutes. Slice cake and drizzle with orange sauce.