01 -
Preheat the oven to 175 degrees C (350 degrees F). Grease a 9-inch round cake pan with butter and line the bottom with parchment paper.
02 -
Peel (or leave skin on) and core apples. Cut into cubes between 1/4 and 3/8-inch in size. Toss in a bowl with apple cider vinegar to prevent browning.
03 -
Mix together the flour, baking powder, and kosher salt in a small bowl.
04 -
In another bowl, beat the butter, 1/2 cup white sugar, and light brown sugar with an electric mixer until light and fluffy.
05 -
Add one egg to the butter and sugar mixture. Beat on high speed until fully incorporated and smooth. Repeat with the second egg.
06 -
Mix in rum and vanilla extract. Add half of the flour mixture and mix until just combined. Fold in the remaining flour mixture gently with a spatula.
07 -
Gently fold the prepared apples into the batter until evenly distributed.
08 -
Transfer the batter to the prepared cake pan. Press the batter in firmly and smooth the top. Dust with 3 tablespoons of sugar.
09 -
Bake in the preheated oven until a skewer inserted in the center comes out clean, approximately 45 minutes.
10 -
Let the cake cool in the pan for 30 minutes. Invert onto a wire rack, then flip back onto a serving plate. Dust the top with powdered sugar before serving, if desired.