I made a recipe that called a tomato sauce that ...

You may have to just add more of all of the ingredients except the lemon zest; there's really no way that I know of to remove only the lemon. Or else if you did not make too fine of a zest you may be able to use a sieve to remove the extra and then try to add more seasoning to help counteract the taste, but the results may be iffy.

You could add carrots or any veggie that has natural sweetness.  Some people add a bit of sugar to tomato sauce to balance the tartness of the tomatoes. You could do that if you haven't already.

If it was too salty, I'd tell you to throw a raw potato in there and let it cook some more. But I think the best solution is to just add more of everything except the lemon, like PGRoot suggested. Obviously you'll need to let it cook some more as well.

If you are going to toss the sauce over pasta or rice the lemon taste would be diminishd. you may have gotten the juice of the lemon into the sauce.