Baked Spiced Aromatic Plums

I am not normally the sort of person who bakes, bottles or otherwise prepares or preserves fruit: I like it ripe, fresh, as it is. I make a couple of exceptions: one for quinces, about which I can grow somewhat obsessive during November; the other for plums. We have a few trees in the garden and from them more fruit that we can eat. Even in a bad year, when the dusty blue, grape-black skins enclose disappointingly unyielding Pucci-green fruit, baking them like this transforms them.