Dear Miss Ginsu,
Ok, I figure if anyone knows the answer to this, it's you.
Spaghetti sauce: aside from adding copious amounts of sugar — how does one keep homemade sauce from being sour/bitter?
I'm assuming this comes from a combination of the tomato sauce and bell peppers? Not sure how to counteract this flavor without turning it into "candied" red sauce.
Cooking all the elements of the process long and slow is a sure-fire way to increase the natural sugars.
Caramelizing the onions so they're nice and brown, getting a little color on the garlic, long-simmering the tomato sauce — not to mention making sure you've removed the skins from the tomatoes... that'll all alleviate bitterness or sour notes. Some people strain out the seeds, too.
So much depends on the quality of the tomatoes you begin with. Since the natural flavors in tomatoes vary so greatly, you can see how it might be difficult to give precise measurements for a sauce recipe.
That said, a *small* amount of sugar added at the end of the process as you're adjusting the seasoning can certainly improve the balance in naturally very acidic or bitter tomatoes.
Though — as you noted — too much sugar just takes the sauce too far down the sweet continuum into candyland.
Also make sure the salt you're using in your recipe isn't "iodized" salt. The iodine that's added to some salt products might protect you from goiters (ew!), but it also adds a note of bitterness. That's just one of the reasons some recipes call for kosher salt.
Hope that helps!