1. Heat a large nonstick skillet or wok over high heat unitl a drop of water sizzles. Add the oil, swirl to coat the pan, then add the steak. Stir-fry until lightly browned, about 4 minutes. Transfer to a bowl.

2. Add the onion and bell peppers to the skillet. Reduce the heat and cook, covered, until the vegetables are softened, about 6 minutes. Uncover and stir-fry until the vegeatbles are browned, about 4 minutes.

3. Meanwhile, whisk together the soy sauce and cornstarch in a medium bowl until smooth; whisk in the broth. return the steak to the skillet, along with the soy sauce mixture. Cook, stirring occasionally, until the sauce boils and thickens, about 3 minutes.