Put a saucepan over a medium flame and bring 2 Qts of water to a boil.
Add the onion, salt and oil to the pan. Cook until the onion is very soft, about 30 mins.
Add the peas and continue to boil for about 15-20 minutes. Add fresh parsley if using as desired.
Drop the pasta into salted boiling water and cook for about half the time of the package instructions. Drain and add it to the peas.
Mix well and serve with a sprinkle of grated pecorino Romano cheese.