Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.
Cream butter and granulated sugar until light and fluffy.
Add egg and vanilla; beat until combined.
In a separate bowl, whisk flour, baking powder, and salt.
Gradually mix dry ingredients into wet ingredients until just combined.
Fold in crushed pineapple and shredded coconut.
Mix brown sugar with 1–2 tsp flour in a small bowl.
Scoop tablespoon-sized dough balls and roll in brown sugar mixture.
Place 2 inches apart on baking sheets and flatten slightly.
Optionally press a maraschino cherry into each center.
Bake 12–15 minutes until edges are golden.
Cool 5 minutes on the sheet, then transfer to a wire rack.
