Destem, wash, and dry your tomatoes whole, then spread them out in a single layer on a baking sheet.
Place the baking sheet in the freezer until the tomatoes are frozen all the way through. This may take anywhere from 2 to 4 hours, depending on size.
Once the tomatoes are rock hard, transfer them to a freeze-proof container or bag and put them back in the freezer.
By doing it this way (instead of just tossing all your tomatoes into bags right away), your tomatoes won’t freeze together into one big clump. Sure, you might have to whack them around a bit if they’ve been frozen for a long time, but you won’t need to thaw out the entire bag just to use a few.
When you need fresh tomatoes in the middle of winter for your soups and stews, pull out as many as you need to thaw and return the rest to the freezer.