Much healthier to make your own, and you can store it in quantities suitable for your needs.
In a large saucepan - add:
One Zuchinni - sliced or diced... however you prefer
One very large sweet or Spanish onion or 2 cooking onions (option B for the UK) - diced, sliced or ground. You can use dehydrated onions if you don't have any fresh handy, about 1/2 cup (100 ml). Onion powder (1tsp or 5ml) is fine too... but avoid onion salt... not so healthy.
One stalk celery, minced finely or chopped. You can use Celery seed(1tsp or 5ml), but again easy on using celery salt.
1/2 to 3/4 cup (150 - 200ml) "Matchstick" or julienned carrots... or one carrot cut as you prefer... remember to do some things differently for texture appeal.
1 tsp. (5 -7ml) oil ... safflower, sunflower, olive or canola are best... or some variation, that includes rapeseed, or flax
1 tbsp (15ml) lemon juice.
Add herbs or spices to your preference such as: oregano, basil, parsley, pepper, tabasco sauce, worcestershire sauce, smoke flavour (very light), jalapeno peppers etc.
(Salt is overused everywhere, so I try to avoid it in cooking)
Add a touch of water (you want it to boil away, or else it will be too runny) and bring to a boil. Reduce heat and simmer for about 10-15 minutes, stirring every 5 minutes or so. Add more water, if you need to.
Prepare to peel tomatoes... about 6 large field or beefsteak size will work. Boil water in a small saucepan. Carefully put in enough tomatoes to sit comfortably beside each other without overcrowding. A big spoon helps so you don't burn yourself. After just a few moments, turn over... you'll notice the tendency they have to just want to stay as they are. A few more moments and you can take them out... I like to put them on a plate. Some folks put them in icy water right away. Now the skins will just easily peel off.
You can either dice them in small or large chunks or puree the tomatoes in a food processor or blender. Set aside for a moment.
roughly 1/2 cup (150ml) sweet peppers - cut the way you prefer... shredded, diced small or in chunks or "julienned" strips. Add color by using green, yellow, red and orange ones. I use my food processor as it only takes seconds, and they're small bits of colour everywhere.
Add peppers and tomatoes to the saucepan... bring to a boil for 5 minutes. Reduce heat and simmer for 10 minutes, stirring frequently. It's done!
Now... You have 2 choices... you can either put them in jars and process with a "boiling bath", or put in freezer jars, and once cool, pop them in your freezer. Freezer method works great for small families, or when someone has to work during dinner... with individual (portion) sizes.
To boil bath:... put sauce in suitable sized canning jars for your needs, leaving 1/4" at the top for air. I use "snap" lid sealers - place them on top with the security rings. The rings stop them from coming off in the water, but don't need to be screwed down tight. When jars are filled, place in a large stock pot or a canning pot that has enough boiling water to cover the jars. When you add the jars, there will be water displacement, so make sure you haven't added too much water.
Boil for 25 minutes... take out and let cool. Lids should 'pop' and be firm to the touch before you put away.
Now you have a healthy alternative to all the sodium and preservatives in store-bought products.
Here's a hint... when making a meatloaf... add a small can of spaghetti sauce... and a can of baked beans... puree them and your picky eaters won't even notice these healthy additives.