In large pot of boiling salted water, cook macaroni until almost tender, 6 minutes. Add broccoli and red pepper; boil until pasta is tender but still firm, 2 minutes. Reserving 1/2 cup (125 mL) liquid, drain and return to pot over medium-low heat. Stir in Cheddar cheese, reserved liquid, cream cheese, onions, Dijon mustard, salt and pepper until melted.
