If the tomatoes are small (e.g. grape, cherry, Roma), cut them in half. If they are larger, cut them in quarters. And, if they’re grande heirloom tomatoes, cut them in sixths.
Place the cut tomatoes in a large bowl, and drizzle with olive oil. sprinkle basil, salt, and pepper over, and gently toss to coat. Place the tomatoes cut side up in one layer on a foil lined rimmed baking dish. (You may need more than one baking dish.)
Roast the tomatoes until they are dry. The small ones will take 2 or 3 hours, while the large ones will take 5 or more hours. Refrigerate and use within 3 days, or freeze for up to 6 months.