In a medium sized skillet or wok over medium high heat add 1 tablespoon olive oil. Add the bell peppers and cook 1-2 minutes until tender. Remove and set aside on a plate.
Turn the heat to high and add the flank steak and cook on each side to sear the beef and reduce heat to medium high and continue to cook until no longer pink and brown on each side.
In a small bowl, whisk the garlic, brown sugar, soy sauce, sesame oil, ginger and cornstarch.
Add the peppers back to the skillet and add the sauce. Let simmer for 1-2 minutes until the sauce starts to thicken. Serve over rice.
Amazing Pepper Steak Stir Fry https://therecipecritic.com/pepper-steak-recipe/