Meanwhile, whisk together the flour, baking soda, baking powder, sea salt, ginger, and nutmeg.
1 ½ cup all-purpose flour, ¾ teaspoon baking soda, ¾ teaspoon baking powder, ½ teaspoon fine sea salt, ½ teaspoon ground ginger, ¼ teaspoon ground nutmeg
In another bowl, combine the melted butter, brown sugar, pineapple juice, eggs, milk, and vanilla extract until uniform. Then add wet mixture to dry mixture and stir until just combined and no dry pockets remain.
¾ cup butter, ¾ cup brown sugar, ¼ cup pineapple juice, 2 eggs, 3 tablespoons milk, 1 ½ teaspoon vanilla extract
Carefully pour cake batter into pan with topping. Transfer pan to the oven and bake on the middle rack for about 40 minutes or until a toothpick inserted into the center of the cake comes out clean.
Let cake sit for about 10 minutes then run a butter knife around the edges of the cake to release any sticky parts from the pan. Invert cake onto a plate by placing the plate on top of the pan then gently flipping it over.
Allow cake to cool to at least 20 minutes then serve warm.