Place raisins in a heat-proof bowl and pour boiling water over them. Allow them to soak until plump (time will depend upon the age of your raisins) and remain in soaking liquid until you are ready to cook.
Wash an apple and remove most of the core, leaving about 1/4-inch at the bottom. Remove a thin strip of peel from around the cavity. Place the apple into a deep microwave-safe baking dish or bowl. Sprinkle the inside with a little cinnamon and fill with drained raisins. Pour a teaspoon of the soaking water over the raisins and drizzle the syrup over the raisins and top of the apple.
Microwave, uncovered, on high power until apple is tender, 3-5 minutes, testing with a fork after 3 minutes. Allow to cool for 5 minutes before serving. (Caution: Inside can be very hot, so do let them cool before eating.)
Variation: Add chopped pecans or walnuts along with raisins.