Bring a large pot of salted water to a boil and cook pasta according to package instructions. Be sure to save 2/3 cup of the pasta water for the sauce.
Meanwhile, add the diced onion, minced garlic and half of the oil to a pan.
Saute for about 5 minutes. Add in the tomato paste and cook for an additional 3-4 minutes.
Transfer to a food processor with all remaining ingredients, including the other half of the oil.
Process until smooth.
Taste and adjust flavors as desired.
Toss with the cooked pasta and serve with extra basil, parmesan and red pepper flakes. Enjoy!