Preheat oven to 350°F (180°C). Grease a 9x5-inch loaf pan and line with parchment. Whisk together flour, baking powder, baking soda, and salt in a bowl.

In a separate large bowl, whisk granulated sugar, oil, eggs, and vanilla until smooth.

Add dry ingredients to wet, stir until just combined, then fold in drained pineapple and the reserved 2 tbsp juice until no dry streaks remain.

Transfer batter to the prepared pan, smooth the top, and bake for 55-65 minutes until golden and a toothpick inserted in the center comes out clean.

While the cake bakes, melt butter and brown sugar in a small saucepan over medium heat, stirring constantly. Add heavy cream, simmer for 2-3 minutes until thickened.

Cool the cake in the pan for 10 minutes, then lift out. Pour the warm glaze over the warm loaf and let set briefly before slicing.