Heat olive oil in a large pot over medium heat. Add onion and garlic; sauté until soft and fragrant, about 3–4 minutes.
Add the tomatoes, water or broth, oregano, red pepper flakes, and a pinch of salt. Stir to combine.
Drop in the broken pasta, pushing it gently under the liquid, until mostly submerged. Bring to a boil, then reduce heat to a simmer.
Cook, stirring occasionally, until the pasta is al dente and the sauce has thickened to cling to the noodles, about 9–12 minutes. If it looks too thick, splash in a little more water.
Stir in fresh basil and grated Parmesan. Taste and adjust salt and pepper. Serve hot with extra cheese on top.