Tortellini with Tomato-Basil Sauce

INGREDIENTS
2 teaspoons extra-virgin olive oil
1 large onion, chopped
1 14-ounce can whole tomatoes, coarsely chopped, juice reserved
Salt & freshly ground pepper, to taste
12 ounces frozen cheese tortellini
1/4 cup chopped fresh basil
1/4 cup freshly grated Parmesan cheese

METHOD
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.