Simmer tomatoes, garlic, and thyme in oil until skins split but tomatoes are still intact, 8 to 10 minutes. Strain, reserve oil, and discard garlic and thyme. Let tomatoes cool completely, then peel. Transfer to a lidded jar; fill with reserved oil. Cover and store in refrigerator up to 1 week or in freezer up to 6 months. Thaw in refrigerator; use for topping a pizza, tossing with pasta, or layering in a sandwich.