Slice the ribeye against the grain into thin strips.
In a small bowl, whisk together the soy sauce, beef broth, brown sugar, minced ginger, minced garlic, and cornstarch to create the sauce.
Heat a large wok or skillet over high heat with the sesame oil. Add the beef strips in a single layer and sear for 2-3 minutes until browned, then remove from the pan.
In the same pan, add the sliced green and red bell peppers and the yellow onion. Stir-fry for 3-4 minutes until slightly tender but still crisp.
Return the browned beef to the skillet. Pour the sauce mixture over the meat and vegetables.
Simmer for 1-2 minutes until the sauce thickens and coats the ingredients evenly.
Garnish with sesame seeds and serve immediately over warm cooked rice.