If you’re using fresh tomatoes, place them in a heatproof bowl large enough to accommodate them and pour enough boiling water over the top to cover the tomatoes. Leave them for a couple of minutes, then drain and make an incision at the top of each. Peel away the skins (or skip this step if you don’t mind skin in the sauce).
Heat the oil in a large saucepan or casserole over a low-medium heat, add the garlic and cook gently for 1 minute, making sure it doesn’t burn. Add the fresh or tinned tomatoes – there’s no need to chop them as they’ll break up during the cooking process. Stir in the oregano and/or basil, season lightly and cook for 30–45 minutes until the sauce has thickened and is a bit chunky, but not soupy. The cooking time will depend on how wide your pan is: the larger the surface area, the faster the liquid in the sauce will evaporate. Taste to check the seasoning and adjust if necessary. Transfer portions into sterilised jars while the sauce is still hot and keep them in a cool, dark place for up to a year, or freeze in containers.