Bring a large pot of water to a boil. While your water is coming to a boil, start the sauce.
Place the olive oil and onion in a large sauté pan. Cook on medium-low until the onion begins to soften. Add the peas and garlic to the onion. Cook until the peas are tender, stirring from time to time, about 10-15 minutes. If the onion begins to stick to the pan, you can add a little water. Taste and season with sea salt and black pepper. Turn heat off and set aside.
Once your pasta water is boiling, season the water with a generous amount of sea salt and add the pasta. Cook until al dente. When the pasta is done cooking, scoop it out of the water and put it directly into the pan with the peas and onion. Stir to combine, adding reserved pasta water as necessary. Finish the pasta with a sprinkle of freshly chopped Italian parsley. And, for those who love cheese, top it with a little Parmigiano Reggiano.