Preheat oven to 350˚F (177˚C). Grease a 9-inch round cake pan with cooking spray or vegetable oil. Set aside.
In a small saucepan over medium heat, melt 4 tablespoons butter and ½ cup light brown sugar. Cook until bubbly and slightly more brown, stirring often. Carefully pour the mixture into the prepared cake pan. Make sure it’s evenly spread.
To make the cake, in a medium bowl, whisk together flour, baking powder and salt. Set aside.
In a large mixing bowl with an electric mixer fitted with a paddle attachment, beat the butter until smooth. Add sugar and beat on medium speed until pale and fluffy, about 5 minutes. Scrape down the sides of the bowl. Add the eggs and beat until smooth, about 1 more minute.
Turn the mixer to low speed, add the flour and ½ cup pineapple juice to the butter mixture alternately in 3 additions, by starting and finishing with the flour. Mix until just combined. Do not overmix.
Roughly drain 7 – 8 pineapple rings and fit them into the prepared cake pan. Spoon the batter over the pineapple and spread evenly. Tap the cake pan lightly on the counter to settle the batter. Bake in the oven until dark golden-brown, about 40 – 45 minutes. Test the doneness with a toothpick. The toothpick should come out clean. Remove from oven and cool in the pan for 10 minutes.
Run a knife around the cake pan and carefully flip the cake pan over onto a serving plate. Slowly lift the cake pan away. Serve the cake warm or at room temperature with vanilla ice cream.