Tortellini with Tomato-Basil Sauce

Put a large pot of salted water on to boil.

Heat oil in a large skillet over medium-high heat. Add onion and cook, stirring, until well browned, about 10 minutes. Add tomatoes and their juice and bring to a boil. Reduce heat to medium-low and simmer, stirring occasionally, until sauce is slightly thickened, 5 to 10 minutes. Season with salt and pepper.

Meanwhile, cook tortellini until al dente, about 5 minutes. Drain and transfer to a large bowl. Toss with tomato sauce and basil. Adjust seasoning with salt and pepper. Serve immediately, passing the Parmesan.