We used to can our family tomato sauce recipe with my mum for years but I have a good reason not to do it any more. While poisoning from botulism from food is rare I've learnt that there is a risk for growing botulism in low acidic food canned in boiling water bath. Tomatoes (to my surprise) aren't highly acidic fruit. Their pH is around 4.5. There are right on the safe edge (high acidity = pH of 4.5 or below). The safest way to can low acidic vegetable, fruit and even meat is in a pressure canner. I am not the owner of one so let's go back to boiling water bath canning method. Unfortunately, any tomato sauce cooked with olive oil, onion and garlic already flavoured and ready to be served isn't safe for canning at home using boiling water bath method. The acidity in this sauce isn't high enough and the other ingredients can create potential danger too. You can still safely can tomatoes at home but it is recommended to follow a tried and tested recipe for canning in a water bath. I like thespruceeats.com basic tomato recipe for canning. It is made purely of tomatoes, salt and uses lemon juice to increase the acidity. It's a great recipe for storing fresh tomatoes from the garden if you've had a big harvest but this sauce isn't ready to be served with pasta so you have to cook it first.