I use both depending on the mood, but I noticed that baking soda neutralises the taste of tomato whereas sugar neutralises the acidic taste.

Coco powder is an option I use as well. A little bit will change the flavor in a nice way. (this is often the secret to real Mexican food)

Tomatoes are already acidic, consider non-lemony tomatoes next time if possible.

As for this batch, both sugar and baking soda works somewhat and you can to both.
A little at a time so you don’t change the taste too much.
Onions are acidic too, but much less so than lemontomatoes, adding a bunch of em to the sauce can help.
If you don’t plan on freezing or canning and you’re just making sauce to put on pasta or something, add cream to it to make a sauce rosée, it’ll mellow the perception of acidity a lot too.
Or use in it a chili where the beans, while not chemically buffering the acidity like baking soda would, can help absorb some of the taste.

Heat and time on the stove.

Sugar for sure. While it can push the edge of sweetness too far if you go heavy, adding a bit at a time will allow you to counter the acid without also changing the rest of the flavor your way bicarb can. Sweetness can be easier to “fix” as well. Up your herbs and spices and the sweetness fades, unlike bicarb which still has that distinct flavor under everything else.