In a bowl, mix sugar and cornstarch. Whisk in coconut milk, broth, soy, curry paste, and lemon peel.
Place an 11- to 12-inch nonstick frying pan over high heat. When hot, add beef. Stir until beef is browned slightly, about 2 minutes. Remove beef from pan.
Add curry mixture to pan. Stir until boiling. Return beef to pan; stir just until hot, about 1 minute.
Mix pasta with cilantro and oil, then pour curry onto pasta.