Step 1

Preheat the oven to 350 degrees F (175 degrees C). Butter a 9-inch round cake pan.

Step 2

Place brown sugar and butter into the prepared pan and place the pan over medium heat. Heat, stirring occasionally, until butter is melted and sugar has dissolved, 3 to 5 minutes. Scatter cranberries over the butter-sugar mixture. Set aside.

Step 3

Mix flour, baking powder, and salt together in a bowl.

Step 4

Beat white sugar and butter together in another bowl using an electric mixer on medium-high speed until light and fluffy, 2 to 3 minutes. Add egg yolks, 1 at a time, beating well after each addition. Add vanilla extract and mix well. Fold in the flour mixture in 3 additions using a silicone or rubber spatula, alternating with milk.

Step 5

Beat egg whites in another bowl using a whisk or an electric mixer until soft peaks form. Add cream of tartar and continue to beat until stiff peaks form. Fold whites into the batter using a spatula. Spoon batter over the cranberries in the cake pan, spreading evenly.

Step 6

Bake in the preheated oven until a toothpick or skewer inserted into the center of the cake comes out clean, 55 to 60 minutes. Transfer the pan to a wire rack and let cool for 15 minutes. Run a knife around the edges of the pan to loosen the cake. Invert onto a serving plate, let stand for 5 minutes, then lift off pan.

Step 7

Whip heavy cream in a bowl using a whisk or an electric mixer until soft peaks form. Stir in confectioners' sugar and vanilla extract.

Step 8

Cut the cooled cake into wedges and top with whipped cream.