Step 1: Preheat your oven to 375°F (190°C). Lightly grease a 12-cup standard muffin tin.
Step 2: In each muffin cup, add 1 teaspoon of melted butter and 1 teaspoon of packed light brown sugar. Gently press one drained pineapple slice into the bottom of each cup on top of the sugar and butter. Place a halved maraschino cherry in the center of each pineapple slice.
Step 3: In a medium bowl, whisk together the all-purpose flour, baking powder, and salt. Set aside.
Step 4: In a large bowl, using an electric mixer, cream together the softened unsalted butter and granulated sugar until the mixture is light and fluffy.
Step 5: Beat in the large egg and vanilla extract until they are well combined. Stir in the 2 tablespoons of reserved pineapple juice.
Step 6: Gradually add the dry ingredients from Step 3 to the wet ingredients, mixing on low speed until just combined and a soft dough forms. Be careful not to overmix.
Step 7: Divide the cookie dough into 12 equal portions. Gently press each portion of dough over the pineapple and cherry in each muffin cup, ensuring the fruit is completely covered.
Step 8: Bake for 12-15 minutes, or until the edges of the cookies are lightly golden brown.
Step 9: Remove the muffin tin from the oven and let the cookies cool in the tin for 5 minutes. This allows the caramelized topping to set.
Step 10: Carefully invert the muffin tin onto a wire rack. If any pineapple or cherry sticks to the tin, gently re-place it on top of its respective cookie. Let the cookies cool completely on the wire rack before serving.