Preheat your oven to 100 deg C (200 deg F). Halve the tomatoes and place them, cut side up, on a lined oven tray. Sprinkle lightly with salt.
Bake until the tomatoes shrivel but before they become brittle (3-5 hours for small tomatoes).
Allow to cool then place in a sterilised jar and top with olive oil. You can add sliced garlic and other herbs if you wish. Store in the fridge.