Directions:
- Make sauce: In a medium bowl, whisk the soy sauce with the vinegar, sugar, and cornstarch. Set aside.
- In a large skillet over high heat, heat 1 tablespoon oil.
- Add flank steak, season with salt, and cook until cooked through and seared on all sides, about 8 minutes.
- Remove steak to a plate.
- Add 1 tablespoon remaining oil and red and green bell peppers to the skillet.
- Cook until softened, about 4 minutes.
- Add the garlic and ginger and cook stirring until fragrant.
- Return the beef to the skillet and pour over the prepared sauce.
- Cook, stirring, until the sauce is glossy about 2 minutes more.
- Serve with rice.
Enjoy.