A very simple recipe pulled from this week's Paleo Solution podcast with Robb Wolf and Greg Everett. I made this earlier today and it was fantastic, and very easy.
1 cup frozen blueberries
Peel the apples and cut them into small chunks. Cook in a saucepan with a little bit of water for about 10 minutes. Blend apples and blueberries (and cinnamon if using) in a food processor or blender. That's it.