Preheat the oven to 350°F (175°C). Meanwhile, heat an 8-inch cast iron skillet over medium-high heat. Add 4 tablespoons butter to the skillet, followed by the reserved juice from the can of pineapple slices and 1/2 cup Golden Barrel dark brown sugar. Stir the mixture continuously until the liquid boils and starts to thicken, which should take about 5-7 minutes. Remove the skillet from the heat and carefully arrange the pineapple rings in the thickened syrup, working from the outside in. If desired, you can place maraschino cherries in the center of each pineapple ring for a classic touch. Place the skillet with the arranged pineapple rings in the oven while you prepare the cake batter.

In a large mixing bowl attached to a stand mixer, or using a hand mixer, beat 4 tablespoons cold butter and 1 cup Golden Barrel light brown sugar together until the mixture is light and creamy. I like to beat the butter for a full minute before adding the sugar—it gives the cake a finer crumb. Add in the eggs one at a time, then mix in the vanilla extract, ensuring everything is well combined.

In a separate small bowl, whisk together 1 1/2 cups all-purpose flour, 1 1/2 teaspoons baking powder, and 1/2 teaspoon salt until evenly combined. With the mixer on low speed, alternately add the dry ingredients and the buttermilk to the creamed butter mixture, starting and ending with the dry ingredients. Mix until just combined, being careful not to overmix the batter to keep the cake tender.

Carefully remove the hot skillet with the pineapple rings from the oven. Pour the prepared cake batter from Step 3 evenly over the arranged pineapples and syrup. Spread the batter gently to cover all the fruit. Place the skillet back in the oven and bake for about 45 minutes, or until the cake is golden and a toothpick inserted into the center comes out clean. To keep the cake extra moist, I sometimes cover the skillet loosely with foil during the last 10 minutes if it starts to brown too quickly.

Remove the skillet from the oven and let the cake cool for 10 minutes. Place a large plate or platter (that is wider than the skillet) over the top of the skillet, then quickly and carefully invert the cake onto the plate. If any pineapple rings or syrup stick to the skillet, simply remove them and arrange on top of the cake. I find letting the cake cool a bit before inverting helps keep the topping from running off.