Preheat oven to 250 degrees Fahrenheit.
In a large pot of boiling water, blanch tomatoes for about 10 to 20 seconds. Remove from water and immediately plunge into an ice bath. When cooled, remove tomatoes.
Peel tomatoes, slice in half lengthwise and remove seeds. Place cleaned tomatoes on a parchment lined baking sheet and season with salt. Add garlic and thyme. Drizzle with olive oil.
Place in oven and allow to cook for 6 to 8 hours. Remove from oven and cool. Refrigerate until ready to use.