Pour the maraschino cherries, including the juice, into a 5x7-inch baking dish. Spoon the cherry pie filling over the cherries and spread into an even layer.
Sprinkle the dry cake mix evenly over the cherry layer. Do not stir.
Slice the butter thinly and place the slices evenly over the cake mix, covering as much of the surface as possible.
Bake for about 50 minutes, or until the top is lightly golden and the filling is bubbling around the edges.
Let the cake cool for 10 minutes before serving. Serve warm, with whipped cream or ice cream if desired.
Notes
Use the correct baking dish: A 5x7-inch baking dish provides the right depth so the cherry dump cake bakes evenly without drying out or overflowing.
Cover the fruit completely: Spread the dry cake mix evenly over the cherry layer so the fruit is fully covered. This helps the topping bake evenly and prevents soggy spots.
Place butter evenly: Slice the butter thinly and distribute it across the surface. Areas without butter can stay dry after baking.
Check for doneness at the edges: The dump cake is done when the top is lightly golden and the cherry filling is bubbling around the edges of the dish.