Hunny why dont you make your own? Why use a jar, with all those syns... its so simple to make your own sauce for a pasta bake.
Chopped onion
3 chopped cloves of garlic
fry until onion soft
then add the tuna and cook through for a few minutes, then add a tin of chopped tomatoes, oregano, marjoram, basil, salt and pepper, a squirt of puree (1/2 syn per person). Simmer for about 15 mins then stir into the pasta and put in a baking dish, and add your reduced fat cheese HeA on top, and bake for 20 mins.
If speed is not the problem, I always cook through diced carrots, mushrooms, sliced celery, diced courgette. Because I like to try and get my 1/3rd of superfree foods in if I can.
Also sometimes I cook mattesons reduced fat smoked sausage (7 1.2 syns total sausage) and lean bacon, instead of tuna. Its a recipe I put in the recipe section called pasta bake deluxe.
You could easily make sauces for pasta bakes in a batch and freeze them!