To prepare sauce, combine in a small bowl soy sauce, lemon juice, and sesame oil. Set aside.
Place a steamer basket in a 12-inch skillet. Add enough water to come just below bottom of basket. Bring to boil, place broccoli in steamer basket, reduce heat to medium low. Cover and steam for 4 minutes. Add sweet peppers. Cover and steam for an additional 3 to 4 minutes or until vegetables are crisp-tender.