I never add sugar but do put a couple of strips of lemon peel in. Let the sauce simmer for a bit to reduce down then remove the peel. Italian granny's tip when making a tomato based sauce for pasta or meat dishes.
Oh come on, albertina,! sugar is sugar whether brown, agave, pomegranate molasses, or coconut... I add about 4 tsp sugar to 8 kg tomatoes when making sauce for winter. It takes the edge off the acidity. But - nina, leave if off completely if you prefer, the sauce is just a bit more sour.