 Throw in the mess of onions with the oil. That's fine. Add the salt at the beginning. I put it on medium just to get things going. And as soon as you start hearing any noise in the pan, turn it down. And I cook onions very low, especially if you want to caramelize them. It's definitely low heat. Stirring them occasionally. But anyone who says medium or medium high, that's just wrong. Because you'll end up, as you said, with burnt onions. It's not your fault. It was just the recipe.