Mix together marinade ingredients and marinate the beef for at least 30 minutes.
2. Sauté beef in non-stick pan over medium-high heat until brown on all sides.
3. Heat up the soybean oil in a wok or large sauté pan, add garlic, ginger, tangerine, and watermelon and sauté for 30 seconds.
4. Add all vegetables, stirring constantly to sweat the onions, and peppers.
5. Stir in the sauce without cornstarch and bring to a boil.
6. Pour in dissolved cornstarch thickening the sauce, add beef and mix thoroughly.
7. Finish with the drops of sesame oil and decorate on plate.