Combine the grenadine and vinegar in a small saucepan and bring to a boil over high heat. Take off the heat and add the chilies and onions. Let sit for at least 15 minutes. Can be made ahead and stored covered in the refrigerator.
For the Tacos:
Combine the SunButter, tamari, mirin, and chili garlic sauce in a medium saucepan and heat over medium heat until the Sunbutter has melted and stir until fully combined. Add the chicken, green onions, and sesame seeds and stir well. Continue cooking until the chicken is heated.
Serve with the Pickled Fresno Chilies and Red Onions, tortilla, and cilantro.