The acidic "bite" is caused by acids in the tomatoes.

The easiest way to avoid it is to add some sugar to the sauce. How much to add is a personal taste thing and depends a bit (I find) on what is also in the sauce, but a teaspoon or two per can is usually plenty. The ingredients in the sauce also play a role as some have different levels of sweetness to them too. For instance onions, you could use red onions (sweet) or a yellow or white (less sweet) and if you caramelize them (rather than just sweat them off), this can alter the taste perception. Other ingredients (e.g. garlic, various types of peppers, and sometimes carrots are common in mine) might also play a role, so test out different ratios and see how you go.

You can't avoid the acid totally, there will always be some acid in tomatoes. There are low-acid tomatoes such as the Roma variety. Some brands of tomato producers use these in canned tomaotes, but as you seem to not be able to specify, this won't be much use to you.

The acidic "bite" is caused by acids in the tomatoes.

The easiest way to avoid it is to add some sugar to the sauce. How much to add is a personal taste thing and depends a bit (I find) on what is also in the sauce, but a teaspoon or two per can is usually plenty. The ingredients in the sauce also play a role as some have different levels of sweetness to them too. For instance, regarding onions, you could use red onions (sweet) or a yellow or white onion (less sweet), and if you caramelize them (rather than just sweat them off), this can alter the taste perception. Other ingredients (e.g., garlic, various types of peppers, and sometimes carrots are common in mine) might also play a role, so test out different ratios and see how you go.

You can't avoid the acid totally; there will always be some acid in tomatoes. There are low-acid tomatoes such as the Roma variety. Some brands of tomato producers use these in canned tomatoes, but as you seem to not be able to specify, this won't be much use to you.