Start by greasing your 6-inch round cake pan with cooking spray. This will help the cake release easily after cooking.
In a small bowl, combine the melted butter, 2 tablespoons of pineapple juice, brown sugar, cinnamon, and nutmeg. Mix until well combined. Pour this mixture into the bottom of the prepared cake pan.
Place the pineapple slices in a single layer over the sugar mixture. Make sure to cover the bottom completely. Nestle the maraschino cherries in the center of each pineapple ring and in any open spots for added color and flavor.
In a large mixing bowl, cream together the softened butter, white sugar, and dark brown sugar until light and fluffy. Add the egg, coconut extract, and lime juice, mixing until well incorporated.
In another bowl, whisk together the flour, baking powder, and salt. Gradually add this dry mixture to the wet ingredients, alternating with the coconut milk. Mix until just combined; be careful not to overmix.
Carefully pour the cake batter over the arranged pineapple and cherries in the cake pan, spreading it evenly with a spatula.
Add 1 cup of water to the bottom of the Instant Pot. Place a trivet in the pot and carefully lower the cake pan onto the trivet.
Close the lid, set the valve to sealing, and cook on high pressure for 40 minutes. Once the cooking time is complete, allow the pressure to release naturally for 10-15 minutes, then do a quick release for any remaining pressure.
Carefully remove the cake pan from the Instant Pot and let it cool for about 10 minutes. Run a knife around the edges to loosen the cake, then invert it onto a serving plate. Let it cool for a few more minutes before slicing and serving.
