Make the marinade: In a medium bowl, whisk the tahini, soy sauce powder, sesame oil, sugar, rice wine vinegar powder, ginger powder, pepper, Sriracha powder and water until smooth. Set aside 2 tablespoons of the sauce and refrigerate. Add the shrimp to the remaining marinade and refrigerate for 30 minutes or up to 4 hours.
Grill the shrimp: Prepare a charcoal or gas grill for medium-hot cooking or place a grill pan over medium-high heat. Brush the grates or grill pan with 1 teaspoon of the canola oil. Remove the shrimp from the marinade, letting the excess drip off, and season with the kosher salt. Grill the shrimp in 2 batches, flipping once, until charred and cooked through, 1½ to 2 minutes on each side. Transfer to a plate and chill.
Wipe the grill clean and prepare for medium-hot cooking. Season the mango and tomato with salt and pepper, and grill, turning once, until charred, 3 to 5 minutes. Set aside and chill.
Bring a medium pot of water to a boil, add the soba noodles and cook until al dente, 3 to 4 minutes. Drain and rinse the noodles under cold water to stop them from cooking. Transfer them to a paper-towel lined baking sheet to dry.
Remove the mango and tomato from the fridge and roughly chop. Set aside.
Taste and adjust the seasoning of the reserved marinade, thinning it out with water as needed. In a large bowl, toss the marinade and noodles to coat evenly. Add the shrimp, mango, tomato, half of the scallions, basil and half of the sesame seeds. Divide the noodles among 4 to 6 plates and top each with some of the remaining scallions and sesame seeds, and serve.
