Start by preheating your oven to 350°F (175°C). While the oven is heating up, grease your 9x13-inch or round baking pan with butter or non-stick spray to prevent the cake from sticking. Make sure to grease it well, especially around the edges.
In a separate bowl, combine ½ cup melted butter and 1 cup brown sugar. Stir them together until the mixture is smooth and well combined. Once mixed, pour it into the bottom of your prepared pan, spreading it evenly.
Then, arrange the pineapple rings on top of the brown sugar mixture. You can add maraschino cherries in the center of each pineapple ring for a festive touch, but that’s totally optional. The pineapple will become the beautiful topping when you invert the cake later!
In another large mixing bowl, combine the yellow cake mix, crushed pineapple (undrained), sour cream, vegetable oil, eggs, and vanilla extract. Using a whisk or electric mixer, beat the ingredients together until the batter is smooth and well mixed. The pineapple adds moisture to the batter, making it incredibly soft and flavorful.
Once your cake batter is ready, pour it evenly over the pineapple rings and brown sugar mixture in the pan. Use a spatula to gently spread the batter if needed, making sure it covers the pineapple rings completely.
Place the pan in the preheated oven and bake for about 35–45 minutes. The cake is done when a toothpick inserted into the center comes out clean. You’ll notice a wonderful aroma filling your kitchen as the cake bakes, and the topping will start to bubble up around the edges.