Mix together the cherry pie filling and cranberry sauce in a bowl. Transfer to a 9-inch pie plate.
Mix together the flour, granulated sugar, baking powder and salt in a bowl. Cut in the butter until it resembles tiny pebbles, about 1 1/2 minutes. Mix in the buttermilk until it just comes together (it will be lumpy).
Dollop 6 to 8 mounds of roughly 2 1/2-inch dough balls around the outside of the pie plate. Sprinkle the coarse sugar over the top.
Bake until the biscuits are golden, 30 to 35 minutes. Cool for 10 minutes before serving.