Cook spaghetti according to package directions. Meanwhile, in a large saucepan, saute garlic in 1 tablespoon butter for 1 minute. Add the cream cheese, sour cream, milk, salt, onion powder, Cajun seasoning, pepper and remaining butter. Cook and stir over low heat just until smooth (do not boil). Remove from the heat.
Drain spaghetti; toss with cream sauce. Sprinkle with parsley.