The Easiest Way To Thicken A Runny Tomato Sauce

A good tomato sauce should be in every cook's arsenal, professional or home. When made well, there's not much else a rich, red Italian sauce needs to become a satisfying meal — perhaps some boiled pasta, crusty bread, a few meatballs. While the list of ingredients needed for a tomato sauce is short, the way they are combined and cooked should require care to ensure each ingredient brings optimal flavor into the mix. When your sauce is thick enough all those tangy, umami, savory, and herby flavors that have blended together can be tasted. But many of them are lost if a sauce is too watery.

Since tomatoes contain a large amount of water, they must be cooked down sufficiently. That's why the best tomatoes for pasta sauce are fleshier and have less water than other varieties, but still need to be thickened to get a consistency that can properly coat pasta. 

Fortunately, thickening a runny tomato sauce is as simple as letting it just simmer for longer. It's not the fastest process and can sometimes take over 20 minutes. However, it doesn't require more than the occasional stir, and as a bonus, the longer you simmer the sauce, the deeper its flavors become. In case it gets too thick, you can always thin it out with some pasta water when combining the sauce with noodles.

Ever noticed how pizza sauce on a baked pizza is so thick? That's because the sauce has reduced by the oven's heat. In fact, a major difference between pasta and pizza sauce is in the consistency, since the former is not usually baked (unless you're baking your pasta dish, in which case the sauce should be slightly runny at the start). 

For most other situations, simply let the sauce simmer on the stove on medium-low heat until the excess water evaporates and the sauce reaches the desired thickness. If you're in a hurry, you can turn your stove to high heat to evaporate the water faster. However, this isn't ideal as you'll have to stir constantly to avoid the sauce at the bottom burning, and might even get splattered by the bubbling liquid.

Of course, since the objective is to evaporate excess water, don't use a cover. If you see thickened bits of sauce that are stuck to the side of the pot, scrape down with a spatula and mix the bits in since they hold a lot of deep flavor. For even bolder flavored red sauce, use tomato paste. This should be part of your sauce's original recipe, but tomato paste can also be used to thicken and add body to runny tomato sauce. When used in combination with reducing the sauce by simmering, it results in a deep flavor that's similar to roasted tomato and a luxurious mouthfeel perfect for slurping with spaghetti.