Bitter Gourd and Beef

I used to buy white bitter gourd and it's not bitter at all. This time, I bought the green and I didn't marinate it with salt after slicing, it's really bitter!
1 big bitter gourd
100g beef, sliced
1 tablespoon soy sauce
1 teaspoon sugar
1 tablespoon cornstarch
1 teaspoon water
1 small red pepper
salt and pepper to taste
sesame oil

Marinate the beef with soy sauce, sugar, cornstarch, and water for 10 minutes. Wash bitter gourd, cut and shred. Heat 2 tablespoon of oil, stir fry bitter gourd. Add light soy sauce, sprinkle with water, sugar, and salt (optional). Set aside. Heat 1 tablespoon of oil, stir fry beef until cook, add bitter gourd. Keep stir fry, add red pepper, sprinkle water (if it's too thick) and sesame oil. Turn off the heat and serve with rice.