pureed apple. I recommend using organic ones cause there's no pesticide, it'll be better for baby. I just cut the apple in half and boil/steam it with a little bit of water. then put it in blender and blend it up (with skin and all). I use blender instead of processer because it shops the skin up and there's no lumps.
My baby also loved pumpkin. Those are the two food I introduced my baby too. I also gave him baby rice cereal but it's bland so I don't do it often.