Heat oil in saucepan over low heat. Add onion and garlic; cook, stirring, occasionally, 12 minutes, until softened, making sure garlic doesn't burn. Add tomatoes, basil, pepper and salt; cook for 25 minutes.
Cook spaghetti in large pot lightly salted boiling water until al dente, firm but tender. Drain well. Toss spaghetti with sauce.
