¼ cup packed brown sugar 1 can pineapple rings 1½ cups all-purpose flour 2 teaspoons baking powder ¼ tsp salt ¾ stick unsalted butter, softened 1 cup granulated sugar 2 large eggs 1 teaspoon vanilla 1 tablespoon dark rum (optional) ½ cup milk 2 Tbs pineapple juice ¼ cup poppy seeds