Fresh Tomato Sauce with Basil Parm

0 Roughly dice the onion, mince or slice the garlic, and cube the tomatoes.
1 Heat the olive oil in a pot over medium heat. Add the onion and garlic with a pinch of salt and cook until softened and fragrant. Add the red pepper flakes and cook briefly.
2 Add the tomatoes and stir well. Cover and cook for about 20 minutes, stirring occasionally, until the tomatoes have completely softened and released their juices.
3 Meanwhile, add the Parmigiano and completely dry basil leaves to a blender or food processor. Pulse until finely crumbled and evenly green. Set aside.
4 Blend the tomato mixture directly in the pot with an immersion blender, or transfer carefully to a blender, until completely smooth. Return to the stove if necessary, then taste and adjust the salt.
5 Cook the pasta in well-salted boiling water until about 2 minutes shy of al dente. Reserve some pasta water, then drain.
6 Add the pasta directly to the tomato sauce and cook until al dente, tossing frequently. Add a small splash of pasta water only if needed.
7 Reduce the heat and toss in the cold salted butter until melted and the sauce becomes glossy.
8 Serve immediately with a drizzle of extra virgin olive oil, plenty of basil Parm, and optional chili oil.