1. Cook edamame according to package directions. Drain. Rinse with cold water; drain.
2. Combine soy sauce and next 5 ingredients (through sesame oil) in a large bowl, stirring with a whisk. Add edamame, tomatoes, cucumber, and onions; toss to coat.
3. Heat a medium cast-iron skillet over high heat. Add olive oil to pan; swirl to coat. Combine steak, salt, and pepper, tossing to coat steak. Add steak mixture to pan; cook 5 minutes or until well browned and crisp, stirring frequently. Spoon 1 1/2 cups edamame mixture onto each of 4 plates; top evenly with steak.