1) To make the sauce, drain and rinse jackfruit well. Blot pieces with a paper towel to remove excess water.
2) In small bowl, stir together water, soy sauce, brown sugar, tomato paste, rice vinegar, sriracha and ginger.
3) Place oil in a medium saucepan and place over medium heat. Add onion and garlic. Sauté 3 minutes. Add jackfruit. Continue to sauté, breaking up pieces of jackfruit with a fork or spatula, until onion is softened and jackfruit is lightly browned in spots, about 3 minutes more. Add soy sauce mixture and bring to a simmer. Lower heat and allow to simmer 15 minutes, until sauce is thick and jackfruit is tender, stirring frequently. While simmering, pull pieces of jackfruit apart using a fork and add more water if the mixture becomes too thick.
4) To make the slaw, stir tahini, rice vinegar, soy sauce and agave or maple syrup together in medium bowl. Thin with water until mixture is easy to stir, but still thick and creamy. Add cabbage, bell pepper, cilantro and scallions. Toss well to coat.
5) Serve by dividing Korean barbecue jackfruit among buns and topping with creamy tahini slaw.