INGREDIENTS
1/4 cup
olive oil
1
medium yellow onion, chopped
5
garlic cloves, minced
1/4 tsp
crushed red pepper flakes
1 28 ounce can
San Marzano whole peeled tomatoes, puréed in a food processor or blender
1/2 tsp
kosher salt
1/4 cup
chopped basil
12 oz
spaghetti
2 tbsp
unsalted butter, cut into pieces
1/4 cup
finely grated Parmesan cheese
Extra basil and Parmesan, for garnish