Preheat oven to 350°F. Grease a 9-inch round or square pan.
Melt the butter and spread it evenly in the bottom of the pan.
Sprinkle brown sugar over the melted butter, then arrange pineapple slices and cherries over the top.
In a large mixing bowl, whisk together the flour, sugar, baking soda, and salt.
Add the pineapple juice, oil or applesauce, vinegar, and vanilla extract. Stir until just combined.
Pour the batter over the fruit layer in the pan.
Bake for 35 minutes or until a toothpick inserted in the center comes out clean.
Allow to cool 10 minutes, then invert onto a plate and serve.