Preheat oven to 250 F degrees. Line baking sheets with parchment paper.
Lay out tomatoes cut side up. Drizzle on olive oil and lightly season with salt and pepper.
Roast for 4 to 6 hours until the tomatoes have shrunk in volume by ⅔ their size and are just slightly juicy.
Video
Notes
If the oven gets too hot prop open the oven door with a wooden spoon.
Roasted tomatoes keep in an airtight container in the fridge for one week or keep frozen for several months. Bring to room temperature before using them.