1. Combine 1 tablespoon vinegar and next 4 ingredients (through black pepper) in a small zip-top plastic bag; add tempeh. Marinate in refrigerator 2 hours, turning occasionally.
2. Combine remaining 2 teaspoons vinegar, honey, juice, canola oil, salt, and red pepper in a small saucepan. Bring to a boil over medium-high heat; cook 2 minutes or until honey mixture is slightly thickened.
3. Preheat grill to high heat.
4. Thread tempeh, tomatoes, mushrooms, and bell pepper alternately onto each of 8 (6-inch) skewers. Place skewers on grill; grill 10 minutes or until browned, turning after 5 minutes and basting occasionally with half of honey mixture. Drizzle with remaining honey mixture; sprinkle with onions.