It's me again!
A couple more thoughts on using your bottled plums.
If the plums are firm you could drain them and make a traditional pineapple upside down cake recipe, swap out the pineapple for the plums.
Drain and puree the plums, use them in place of the applesauce in a traditional applesauce cake recipe or in place of the pureed bananas in a banana bread or cake.
You could also puree the drained prunes and use them as a substitute for half of the oil or butter in a spice cake, chocolate cake or brownie recipe.