Soak 6 long bamboo skewers in cold water for 30 minutes or use 6 long metal skewers.
Thread tofu, bell pepper, mushrooms and tomatoes alternately on skewers. Place in single layer in large glass baking dish. In small bowl, whisk together soy sauce, lime juice, brown sugar, sesame oil and garlic. Pour over skewers and let stand 1 hour, turning occasionally.
Meanwhile, make Ginger-Cashew Sauce: In food processor, place cashews and pulse on and off until ground; set aside. In medium saucepan, heat sesame oil over medium heat. Add scallions, garlic and ginger and cook, stirring often, 30 seconds. Stir in ground cashews, soy sauce, coconut milk and hot sauce. Reduce heat to low and simmer, stirring occasionally, 30 to 45 minutes, adding up to 1/3 cup water if mixture seems too thick. Remove from heat and set aside.
Prepare grill. Place marinaded skewers on grill, reserving marinade. Cook until lightly browned, turning occasionally and basting with marinade, 12 to 15 minutes. Transfer to serving platter and garnish with cilantro if desired. Serve hot, with Ginger-Cashew Sauce for dipping.