For baked apples, you'll want an apple variety that is firm and holds its shape once baked, like Honeycrisp, Golden Delicious, Cortland or Granny Smith. You want to avoid varieties that get soft and mushy when baked. It also depends on the flavor you prefer. Granny Smith will be more tart, while Honeycrisp will be sweet. I used SweeTango in this recipe which is a cross between Honeycrisp and Zestar apples, so they're crisp and sweet.