1 lb. spaghetti
2 tbsp. extra-virgin olive oil
1 small yellow onion, chopped
3 cloves garlic, minced
4 medium tomatoes, chopped (about 4 c.)
Freshly ground black pepper
Pinch crushed red pepper flakes
2 tbsp. thinly sliced basil, plus more for garnish
Freshly grated Parmesan, for garnish
In a large pot of boiling salted water, cook pasta according to package directions. Reserve ½ cup of pasta water, then drain.
In another large pot over medium heat, heat oil. Add onion and cook until soft, 5 minutes. Add garlic and cook until fragrant, 1 minute more.
Add tomatoes and cook until juices are released. Season with salt, pepper, and a pinch red pepper flakes. Reduce heat and let simmer for 15 minutes. Stir in basil.
Add spaghetti and ¼ cup pasta water. Toss to combine. Add more pasta water to bring sauce together as needed.
Garnish with more basil and Parmesan before serving.