Preheat oven to 350°F. Grease a 13x9 inch pan with cooking spray.
Spread the pineapple and its juice into the bottom of the pan. Dollop the cherry pie filling on top and spread gently across the pineapple.
Pour the dry yellow cake mix on top and spread it evenly over the top. Place the slices of butter on top of the cake mix so that they cover the entire pan.
Place the pan in the oven and bake for 25 minutes. Remove the pan and sprinkle the chopped pecans over the top. Bake for 15 minutes more, or until the top is lightly golden. The center will still jiggle a little in the middle when it’s done—and that’s ok!
Let the dump cake cool slightly, then serve warm with vanilla ice cream on top.
You can substitute peach or blueberry pie filling for the cherry pie filling. Instead of ice cream, whipped cream is also delicious on top!