At first glance that looked like a gall, but magnolias seldom get galls. Galls are usually caused by insects that lay eggs in a stem or leaf of a plant and the plant then surrounds the injury with growth, forming a gall. If you cut one open, you will see a larval insect, if it is in fact a gall.   Yours are at the end of a stem. This suggests that what you have are seed pods. As these mature, they appear scale-like and eventually split apart and seeds, covered in a red flesh appear.   You would see the ripening seeds when you cut one open.  I found another ask an expert question that had photos very similar to yours and that was answered as seed pods also.