Along with other home made sweet spreads, jars of apple butter must be processed in a boiling water bath for safety. It is possible for jars to seal when food is packed hot. However, such seals are usually weak and likely to fail in a short time. Canned breads and cakes. Home canned quick breads and cakes pop up every few years.
Recipes call for baking the product in a canning jar and then topping with a two piece lid.
Heat from the baked product produces a weak seal on the hot jar. There are a number of risks associated with this kind of product. Canning jars are not designed for oven use. Jars could break, perhaps explosively, in the oven or when taken from it. These foods are also low-acid, high moisture foods.