Boil the water in a medium saucepan. Add the tomatoes and simmer for 2 minutes. Drain immediately and layer the tomatoes between 2 double thicknesses of paper towels, changing the paper several times, until the tomatoes are dry. (It is sometimes easier to blanch and dry them in 2 batches.)

Layer the tomatoes, garlic, rosemary, oregano, and peppercorns if using in a 2- to 3-cup jar with a tight lid. Pour enough olive oil in the jar to reach the top and completely cover the tomatoes. Cover the jar and let sit overnight in the refrigerator. Before using, bring to room temperature, then blot the tomatoes with paper towels to remove excess oil.