Preheat oven to 350 degrees and line the bottom of a 9" x 13" cake pan with parchment paper. Coat with cooking spray and arrange drained pineapple evenly in a single layer across the bottom of the cake pan.
Drizzle melted butter over pineapple then sprinkle brown sugar evenly over the pineapple slices and set aside.
In a large mixing bowl, whisk the sugar, oil and eggs together until completely blended. Add the carrots to the bowl of a food processor fitted with the steel blade and pulse until the carrots are very finely chopped and resemble the texture of wet sand. Add carrots to wet ingredients and stir to combine.
Sift the flour, baking soda, salt and cinnamon on top of the wet ingredients and carefully fold until completely blended.
Pour carrot cake batter into prepared cake pan, being careful not to allow the batter to push the pineapple to one side or the other. Bake 50-55 minutes or until center is firm and a toothpick comes out with a few moist crumbs attached.
Remove from oven and allow cake to cool for about 5 minutes before inverting onto a platter or tray. Allow cake to continue to cool on the platter and serve when slightly warm or at room temperature.
One Last Thing
Remember to arrange the pineapple rings at the bottom of the pan nicely because that will be the presentation side of your cake.