We had another Cousinentreffen (cousins-get-together) last night and ended up exchanging Grandma's (?) recipe for plum jam cooked for 8 hours IN the oven not on top (and stirring for hours and hours).
This certain kind of jam is called Latwerge here. Love it or hate it.
I make mine in the bread machine and I don't use sugar, only plums and spices. I eat it faster than I can cook it in summertime - no sugar needed. I love the pure taste of mine.