01 - 
                Cut the sirloin into thin 1/2-inch strips against the grain. For easier slicing, chill in the freezer for 20 minutes until firm.
              
              
              
                02 - 
                Whisk together soy sauce, sugar, cornstarch, and ground ginger until smooth and fully dissolved.
              
              
              
                03 - 
                Coat beef strips in the marinade and let rest 15 minutes at room temperature or up to 2 hours refrigerated.
              
              
              
                04 - 
                Heat 1 tbsp oil in a wok over high heat. Cook beef in small batches for 3 minutes until caramelized but still tender inside. Remove and set aside.
              
              
              
                05 - 
                Add remaining oil to the wok. Stir-fry red onions for 2 minutes until slightly softened but crisp.
              
              
              
                06 - 
                Toss in the green bell pepper and stir-fry for 2 minutes, keeping them bright and crunchy.
              
              
              
                07 - 
                Add tomato wedges and return beef with juices to the wok. Toss for 1–2 minutes until tomatoes release juices and sauce thickens.
              
              
              
                08 - 
                Transfer to a serving plate and garnish with green onions if desired. Serve hot with steamed rice or noodles.