Steam tempeh over boiling water in steamer basket 10 minutes to reduce bitterness and help absorb sauce.
Meanwhile, whisk soy sauce, vinegar, syrup, sesame oil, and cornstarch in small bowl; set aside.
Heat vegetable oil in large wok or skillet over medium-high; cook tempeh 5-6 minutes until golden brown all over, stirring occasionally.
Add broccoli and pepper; stir-fry 4-5 minutes until tender-crisp.
Add garlic and ginger; cook 30 seconds until fragrant.
Pour sauce over; toss to coat. Cook 2-3 minutes until thickened and glossy.
Remove from heat; garnish with green onions and sesame seeds. Serve immediately over rice or noodles.