That is an interesting point. I know that a lot of marinara sauces call for carrots, usually shredded, but I never thought to make a connection between the carrots and sweetness. I also know that carrot juice is very sweet, having made it many times with a juicer. That led me to wonder whether carrot juice has ever been recommended for tomato-based sauces. From a Google search, I found that it has, typically as a substitute for some of the water used in the sauce. I also found a recipe for California pizza using carrot juice in the dough and carrots (shredded) in the tomato sauce. The juice is used in lieu of the water in the dough (a little bit of it is warmed and used to proof the yeast).