In a large stockpot heat 2 tablespoons of olive oil over medium heat, add onions sauté until translucent. Add garlic, sauté for a few minutes just until soft, making sure it does not burn. Add diced tomatoes, remaining 2 tablespoons of olive oil, salt and pepper to taste, mix well.
Bring mixture to a boil then reduce the heat to low, simmer until tomatoes soften and release their juices about 20-30 minutes. Add julienned basil, adjust salt and pepper to taste, and mix well.
Prepare pasta according to package directions. Serve over prepared spaghetti, and top with parmesan cheese as desired. Enjoy!