In a large skillet, heat the olive oil over medium heat.
Add the chopped onion and sauté for 2-3 minutes, or until softened.
Add the minced garlic and cook for another 1-2 minutes, or until fragrant.
Add the diced tomatoes, tomato paste, dried oregano, salt, and pepper to the skillet. Bring the sauce to a simmer and cook for 5-7 minutes, or until slightly thickened
Add the zucchini noodles to the skillet and toss to coat with the sauce. Cook for 2-3 minutes, or until the zucchini noodles are tender.
Divide the zucchini noodles and tomato sauce among 4 plates. Garnish with chopped fresh basil, if desired.