Boil the spaghetti in salted water until almost al dente. Save 1 cup of pasta water, then drain.
While the pasta cooks, heat the olive oil in a large pan over medium-low heat. Add the garlic and cook until fragrant and lightly golden.
Add the tomatoes, salt, pepper, and oregano. Cook for 8–10 minutes, gently crushing some tomatoes with a spoon.
Add the spaghetti to the sauce and toss well. Add a little pasta water if it looks dry.
Taste, adjust seasoning, and serve with grated parmigiano or pecorino cheese.