Don’t Waste Tomato Paste on the Pot
Anyone who has ever made a tomato-based pasta sauce has probably noticed the thick, dark red mark the sauce leaves on the sides of the saucepan as it diminishes. This sticky residue is (free! Bonus!) Tomato Paste that should never be discarded.
One of the main reasons we cook tomato sauce for so long is because we displace the water and concentrate the flavors, and by not adding the pasta to the sauce, you leave that concentrated flavor, which I’m sure you don’t want to do.
There is a simple solution to this: simply scrape along the side of the pan until the sauce is reduced, adding the pasta back to the boiling mass of the tomatoes from which it was obtained. In terms of pace, I like to check the pasta every 15 minutes or so; The paste will eventually dry out if you leave it on the side of a hot pot for too long, making it difficult to remove (and can taste burning).
But even too dry, sticky paste is not useless. I found it to be fairly easy to wipe off with a slice of tomato stew. Just take a large piece of tomato with tongs and rub it over the edge of the pan; the heat and moisture radiated from it immediately steam away the sturdy paste, ensuring that no odor remains. Toss the tomato pasty back into the sauce, let the whole thing decrease a little, and repeat until you reach the desired level of zest.