Preheat oven to 350°F and line a baking sheet with parchment paper.
Cook apples: Heat diced apples with maple syrup, cinnamon, lemon juice (and zest), and a pinch of salt in a pan for 6–8 minutes until soft. Cool in the freezer.
Make dough: Mix protein powder, oat flour, oats, Greek yogurt, and honey in a bowl. If the dough feels too dry, add the optional milk.
Combine: Fold in the cooled apples. Roll into 10 balls and place on the baking sheet.
Bake for 12 minutes.
