Warm a 10-inch noncorrosive sauté pan. Add the butter and melt until lightly brown. Add the onion and garlic; cook until translucent. Add the stock and cook until three-fourths reduced. Add the penne. Toss and cook for 3 to 4 minutes. Add the cream and the cheese. Bring to a boil; cook 2 minutes. Add the lemon juice to thin the texture slightly. Season with the pepper and sprinkle with the parsley.
Serve with warm, crusty bread and a spinach salad.