Heat oil in a nonstick skillet over medium heat. Add onion, celery, carrot, and tempeh, and sauté 5 minutes. Stir in tomatoes and next 6 ingredients (tomatoes through salt). Bring to a boil; cover, reduce heat, and simmer 10 minutes, stirring occasionally. Uncover and cook an additional 3 minutes or until mixture is slightly thick. Serve on hamburger buns.