Step 1: Prepare your canning equipment. Wash and sterilize 7 quart-sized canning jars and keep them warm. Warm new lids in hot (not boiling) water. Gather your water bath canner, rack, jar lifter, funnel, and ladle.
Step 2: Wash tomatoes thoroughly. Score an 'X' on the bottom of each tomato, then blanch them in boiling water for 30-60 seconds. Immediately transfer to an ice bath. Peel, core, and chop the tomatoes into manageable pieces. You may also use a food mill to remove seeds and skins for a smoother sauce.
Step 3: In a large, heavy-bottomed pot, heat olive oil over medium heat. Add chopped onions and cook until softened and translucent, about 8-10 minutes. Add minced garlic and cook for another 1-2 minutes until fragrant.
Step 4: Add the prepared tomatoes, fresh or dried basil, oregano, dried thyme, bay leaves, salt, pepper, and optional tomato paste to the pot. Bring the mixture to a boil, then reduce heat to low and simmer gently for at least 2-3 hours, or until the sauce has thickened to your desired consistency. Stir occasionally to prevent sticking.
Step 5: Taste the sauce and adjust seasonings if necessary. Remove bay leaves. For safe canning, add 1 tablespoon of bottled lemon juice or 1/2 teaspoon of citric acid directly to each quart jar (or 1/2 tbsp lemon juice/1/4 tsp citric acid for pint jars). Do not reduce the amount of acid.
Step 6: Ladle the hot sauce into the hot, sterilized jars, leaving 1/2 inch of headspace. Remove any air bubbles by running a clean, non-metallic utensil around the inside of the jar. Wipe the jar rims clean with a damp cloth.
Step 7: Place warm lids on the jars and secure with bands to fingertip-tight. Place the filled jars on the rack in the water bath canner, ensuring they are fully submerged by at least 1-2 inches of water. Bring the water to a rolling boil.
Step 8: Process quart jars for 40 minutes (or pint jars for 35 minutes), adjusting for altitude if necessary. Once processing is complete, turn off the heat, remove the canner lid, and let the jars sit in the hot water for 5 minutes.
Step 9: Carefully remove the jars with a jar lifter and place them on a towel-lined counter, spaced apart, to cool undisturbed for 12-24 hours. Do not retighten bands.
Step 10: After cooling, check seals. The center of the lid should be concave and not flex when pressed. Remove bands, wipe down jars, label with contents and date, and store in a cool, dark place. Any unsealed jars should be refrigerated and used within a week.