Of course. Just wash them and remove the stalks. We then halve them, and remove the stones, but this isn't essential. But halving them does give an opportunity to discard any that are infested, and to cut out any minor blemishes.
We normally microwave a couple of pounds at a time in a Pyrex bowl. Put the oven on a lowish setting, say 3 or 4, so that the heat has a chance to go all the way through (otherwise there's a danger of boiling the outside ones and leaving the inner ones unheated.
We'd start with 3 minutes at the low setting, and stir them gently and pop them back for a little longer if necessary. That's in a 1000 watt oven. Different quantities and different powered ovens will need longer or shorter times. Just keep an eye on them and you'll find the right settings for your setup.
That way the plums remain in halves, and aren't cooked to a slop. You can add a little sugar before cooking if the plums are a sour variety.
If we're processing a lot, we'll microwave a couple of pounds at a time, and put them together into a big bowl to cool (covered with clingfilm). Then they can be doled out into ziplock bags or cliptop containers for freezing.
