Preheat the oven to 375ºF. Line a 12-cup muffin pan with paper liners. Peel, core, and chop the apple into large chunks. Add it to the blender along with other ingredients and blend on high speed until smooth. Divide the batter evenly among the prepared muffin wells and bake for 15 to 20 minutes. Once the tops are set and not jiggly, remove the pan from the oven and let cool.