1. In a deep skillet over medium heat add the olive oil and warm it until it is beginning to bubble. Then add the onion and cook until it is very soft, about 10 to 12 minutes. Then add the garlic cloves and stir them in for about 2 minutes, followed by the red pepper flakes and stir for 1 more minute.

2. Carefully pour the tomatoes into the onion mixture and add some kosher salt. Reduce the heat to low and simmer the sauce for about 15 minutes, or until the sauce thickens slightly. Stir in the basil leaves and turn off the heat.

3. Cook the pasta for about 10 minutes in salted boiling water, drain it – RESERVE 1 cup of the pasta water – and add it to the tomato sauce in the skillet.

4. Bring the tomato sauce up to a bubble over medium-high heat and cook the pasta for an additional 3 minutes, until it has completely cooked is is al dente. Remove the pan from the heat and discard the basil leaves. Stir in the cubed butter and Parmesan cheese. Toss well and serve.