Start your Spark and set it to 600°F.
Season the shrimps with a sprinkling each of salt, pepper and sumac and place them on the skewers.
Brush the tomato slices and jalapeños with olive oil. Place the tomatoes, jalapeños, scallions and shrimp skewers on the grill and cook for about 10 minutes, until the shrimp are cooked through and the skins of the vegetables are nicely charred. Chop up the jalapeños.
Open a pita to create a pocket. Spread the sour cream inside each pita and then stuff the pita with all the grilled goodies.