Preheat your oven to 400 F. Line a small baking sheet w parchment paper.
Place your apple slices onto the baking sheet and brush or drizzle with the melted butter. Use your hands to get them coated all over. Sprinkle with cinnamon and bake for 10 minutes. Remove from oven and flip each slice over. Sprinkle this side with cinnamon and continue to bake for another 5-7 minutes.
Transfer to your plate and enjoy! Some of us love this with a nice scoop of vanilla ice cream!