Summertime Pineapple Upside-Down Cake

Melt 2 tablespoons of the butter in a large skillet over medium-high heat. Add the pineapple, brown sugar and 1/4 teaspoon salt, and cook, tossing occasionally, until the sugar dissolves in the pineapple juices and reduces to a thick sauce, about 8 minutes. Scrape the pineapple and sugar syrup onto a plate, spread out in a single layer, and let cool to room temperature, about 10 minutes. Once the pineapple mixture is cool, transfer it to the bottom of the prepared pan and smooth into an even layer or arrange in concentric circles or tiled rows, whatever you like. Place the pan in the refrigerator to firm the syrup while you make the cake batter.