Creamy tomato sauce + penne pasta = a meal you can master

1tablespoonunsalted butter

1?2medium onion, cut into small dice (1/2 cup)

1tablespoontomato paste

1clove garlic, minced

1?4teaspoonsalt, plus more for the pasta cooking water

1?2teaspoonsugar

Pinch crushed red pepper flakes

One 14.5-ounce can crushed or diced tomatoes, and their juices

2tablespoonssour cream (may substitute cream cheese, heavy cream or half-and-half)

1pounddried penne pasta

1ouncepecorino Romano cheese, grated for serving

Melt the butter in a large saucepan over medium heat. Stir in the onion; cook for 5 to 8 minutes, until the onion softens and becomes translucent. Add the tomato paste, garlic, salt, sugar, and crushed red pepper flakes; cook for about 1 minute, until the garlic becomes fragrant. Add the tomatoes; once the mixture begins to bubble at the edges, partially cover and cook for about 5 minutes, until slightly thickened. Reduce the heat to low, then stir in the sour cream until well blended. Keep warm over low heat.

Bring a pot of generously salted water to a boil over medium-high heat. Add the pasta; cook for 2 minutes less than the package directions indicate (to al dente consistency). Before draining the pasta, reserve 1/2 cup of the pasta cooking water. Return the drained pasta to the pot.

Pour the warm sauce over the pasta and toss to coat, then add 1/4 cup of the reserved pasta cooking water, stirring to incorporate. Cook over low heat for 2 minutes, stirring and adding some or all the remaining pasta cooking water, as needed, to achieve the sauce consistency you prefer.

Divide among individual bowls. Top each portion with grated cheese, and serve hot.