Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes or until al dente; drain.
While pasta water is boiling, heat olive oil in a large skillet over medium heat. Cook onions in oil until tender. Stir in salt, pepper, tomato sauce, water and peas. Reduce heat and simmer until pasta is done.
Stir cooked pasta into tomato mixture. Increase heat and bring to a boil briefly. Remove from heat, stir in cheese, cover and let rest 10 minutes. Serve.