Slice the tomatoes in half. Put them in a baking dish and pour over the olive oil. Add the salt and pepper and toss together gently.
Roast 2-3 hours, until the tomatoes become shriveled, lightly caramelized and their juices have collected in the dish.
Use right away, or cover and refrigerate up to a week.
Notes
This recipe is easily multiplied if you have a bigger batch of tomatoes to preserve. Be sure to use a baking dish or baking sheet large enough to fit them in one layer (or use multiple).
Add a small pinch of sugar if your tomatoes taste acidic.
For more flavor, stir in a clove of finely chopped or grated garlic when the tomatoes come out of the oven and stir in some chopped fresh herbs such as thyme, oregano or basil.
Storage: If you don't use them up within a day, keep the tomatoes in a covered container in the fridge for up to 1 week. Drizzle olive oil over the surface of the tomatoes before storing to help keep them fresher. The tomatoes can be frozen for 1 month. Make sure to package them in an airtight container before freezing.