Preparation Preheat oven to 350°F with rack in middle. Melt butter in skillet over medium heat, then stir in brown sugar, rum, and a pinch of salt and simmer, stirring, 4 minutes. Remove from heat and arrange bananas on top of sugar mixture in concentric circles, fitting in as many pieces as possible. Whisk together flour, baking powder, cinnamon, nutmeg, and salt. Beat together butter and sugar with an electric mixer at high speed until pale and fluffy, about 3 minutes. Add eggs, 1 at a time, beating well after each addition. Beat in rum and vanilla. Reduce speed to low and add flour mixture in 3 batches, alternating with milk, beginning and ending with flour, mixing until just incorporated. Spoon batter over bananas, smoothing top, and bake until top is golden and a wooden pick inserted into center comes out clean, 40 to 45 minutes. Let cake stand in skillet 5 minutes. Invert a plate over skillet and invert cake onto plate (keeping plate and skillet firmly pressed together). Replace any banana stuck to bottom of skillet. Serve cake slightly warm or at room temperature.
Preparation Preheat oven to 350°F with rack in middle. Melt butter in skillet over medium heat, then stir in brown sugar, rum, and a pinch of salt and simmer, stirring, 4 minutes. Remove from heat and arrange bananas on top of sugar mixture in concentric circles, fitting in as many pieces as possible. Whisk together flour, baking powder, cinnamon, nutmeg, and salt. Beat together butter and sugar with an electric mixer at high speed until pale and fluffy, about 3 minutes. Add eggs, 1 at a time, beating well after each addition. Beat in rum and vanilla. Reduce speed to low and add flour mixture in 3 batches, alternating with milk, beginning and ending with flour, mixing until just incorporated. Spoon batter over bananas, smoothing top, and bake until top is golden and a wooden pick inserted into center comes out clean, 40 to 45 minutes. Let cake stand in skillet 5 minutes. Invert a plate over skillet and invert cake onto plate (keeping plate and skillet firmly pressed together). Replace any banana stuck to bottom of skillet. Serve cake slightly warm or at room temperature.