Preheat the oven to 350 degrees F. Spray 2 (9-inch) round cake pans with nonstick cooking spray and coat with flour.
In a large bowl, beat 1 cup butter at medium speed with an electric mixer until creamy. Gradually add the sugar, beating until fluffy. Add the eggs, 1 at a time, beating well after each addition. Stir in the vanilla and set aside.
In a small bowl, add the 3 cups of flour, baking powder, and salt. Stir to combine. Add the flour mixture into the egg mixture alternately with the buttermilk, beginning and ending with the flour mixture.
Divide the brown sugar evenly into each pan. Pour the melted butter equally over the brown sugar. Arrange the pineapple slices and cherries over the brown sugar. Reserve remaining pineapple slices and cherries for another use.
Pour equal amounts of batter over the fruit and bake until a wooden pick inserted in center comes out clean, about 40 to 45 minutes. Let the cakes cool in the pans for 10 minutes. Invert the cakes onto wire racks to cool completely.
To assemble the cake, carefully arrange 1 cake layer, pineapple side up, on a cake plate. Carefully stack the remaining cake layer, pineapple side up, over the first layer. Frost the sides of the cake with Pineapple Buttercream Frosting. Press chopped pecans into sides of cake, if desired.
Beat all the ingredients in a large bowl until well combined.
This recipe has been updated and may differ from what was originally published or broadcast.