An apple is a delicious, crunchy addition to any cranberry relish! To maintain a nice balance of sweetness, choose apples such as Red Delicious, Honeycrisp, and Fuji. All are on the sweeter side. No need to peel the apple, but core it first to keep the seeds out of the relish. You don't need an apple coring tool, I simply cut large pieces away from the core with my chef's knife.