Due to the addition of the fruit preserves, it is hard to reheat these cookies. If you would like the cookies to be warm, then the best recommendation is to preheat the oven to around 325 degrees Fahrenheit and place them on a greased cookie sheet. They should be in there for only 2 to 3 minutes, checking them frequently to make sure the jam has not oozed out. It is best to do this after they have been frozen to reduce the chances of this. From here, you remove them, add more jam if you wish, and re-dust with powdered sugar.