Q: When I watch cooking shows, they allow their spaghetti sauce to come to a boil. Doesn't that break the sauce and make it watery when you plate it? It has always been my understanding that spaghetti sauce should always be heated to just under boiling point.
A: On TV, cooking is all about flashing knives and bubbling pots. So there are things that TV cooks do that aren't necessarily how you'd do it at home.
However, I checked a number of sources and couldn't find anything about tomato sauce becoming watery when it's boiled. You do need to be careful about cooking tomatoes over high heat, though. The sauce could easily burn and stick.
If you're having trouble with watery tomato sauce, it might be the tomatoes, according to Miriam Rubin, the author of "Tomatoes: A Savor the South Cookbook" (UNC Press, 2013).
"If she made her sauce without using any paste tomatoes (or without seeding the tomatoes), that sauce will be more watery," says Rubin. "I always use a combination of big slicers, paste tomatoes such as Amish Paste, Oxheart or Opalikia for sauce and I add (tomato) paste to thicken it."
Spaghetti also can be watery if you don't drain the pasta well. Using a little of the starchy pasta cooking water can help thicken sauce, or you can drain the pasta and stir it into the sauce to coat it before piling it on the plate.