Scoop ½ cup of the hot broth into a small bowl with the miso paste. Stir until combined and return it to the soup pot. Add the turmeric, black pepper, lemon and lime juice, coconut oil, tamari, sriracha, tofu, noodles, and bok choy. Simmer for 10 minutes. Season to taste with ¼ teaspoon sea salt, if desired, and serve with fresh herbs, if desired.