Pour the melted butter into your cake pan and swirl to coat the bottom. Sprinkle the brown sugar evenly over the butter. Arrange pineapple rings over the sugar layer. Place a maraschino cherry in the center of each ring. Set aside.
In a bowl, cream the softened butter and sugar together until light and fluffy. Beat in the eggs one at a time, then stir in the vanilla. In another bowl, whisk together flour, baking powder, and salt.
Gradually add the dry ingredients to the wet mixture, alternating with the milk and pineapple juice. Mix until smooth and just combined.
Pour the batter gently over the pineapple layer in the pan, spreading evenly with a spatula. Bake in a preheated oven at 350°F (175°C) for 40–45 minutes, or until a toothpick inserted in the center comes out clean.
Let the cake cool for 10 minutes in the pan. Run a knife around the edges to loosen. Carefully invert onto a serving plate. Let cool slightly before slicing.