Bring a large pot of water to a boil over high heat and salt liberally. Add the pasta and cook according to package instructions. Drain, reserving 2-3 Tbsp. of the cooking liquid, and set aside.
While the pasta is cooking, heat the olive oil in a large saucepan. Sauté the onions and garlic for two minutes or until fragrant.
Add the onion mixture to a blender along with the remaining ingredients. Blend until smooth. Return to the pan and bring to a simmer. Cook for five minutes. Off heat, add the macaroni and toss to coat. Garnish with fresh, chopped parsley.