Preheat oven to 350F. Mix up your dry cake mix according to directions on box. In a 13x9 dish place your 1 1/2 sticks of butter and set this in the hot oven to melt them completely. Watch carefully.
Pull the pan out of the oven and spread the pineapple & juice all in the hot pan and sprinkle evenly the brown sugar all over, then pour your cake batter over the brown sugar.
Bake for 35 minutes or until cake tests done in the center with a toothpick or wooden skewer. I take a cookie sheet and flip the cake over immediately (Quickly & Carefully not to get burned using thick pot holders or silicone mitts) let cool. Enjoy!