Coat the top sirloin steak generously with freshly ground black pepper, massaging it gently. Proceed to dice the steak into cubes or slice it into strips as per your preference. Place the steak in a 6-quart slow cooker along with the diced onions and bell peppers.
In a separate bowl, whisk together 1 cup of beef broth, soy sauce, brown sugar, ground ginger, and garlic powder. Pour this mixture over the contents in the slow cooker.
Mix the remaining 1/2 cup of beef broth with cornstarch and add it to the slow cooker. Stir the contents thoroughly to ensure a uniform mixture.
Seal the lid on the slow cooker and set it to cook on low heat for a culinary journey of 5 hours. As a final touch, taste the dish and adjust the seasonings according to your preference.