In a small bowl, combine the onions and sumac and toss well. Set aside until ready to serve.

In a large bowl, combine the lamb, onions, parsley, garlic, and kirmizi biber, and mix thoroughly, kneading with your hand. Add the egg white and salt, and knead mixture to a paste. Divide it into 4 equal portions, and roll each portion into a flat, sausage shape.

Wipe kebab skewers with oil, and using a dampened hand gently squeeze meat against the skewer. Secure meat onto skewer by squeezing mixture up and down, spreading it evenly and making sure it is firmly attached to the skewer.

Preheat a grill to medium high heat and brush it with oil. Roast the poblano chiles over the grill. Keep turning so the skin is evenly charred, without burning and drying out the flesh. Transfer charred peppers to a plastic bag, tie the top closed and let steam until cool to the touch, about 15 minutes. Peel off the charred skin by hand. Cut away stems, seeds and veins, and halve them.

Heat the flat bread or pita until warm but not crisp, cut into cubes and wrap in foil to keep warm.

Grill the kebabs, brushing them with the melted butter, about 2 to 3 minutes per side. Grill the tomato halves at the same time.

To serve, place the bread cubes on a serving platter or individual plates, drizzle with melted butter, remove meat from skewers and place over bread. Top with roasted peppers and tomatoes, drizzle with more butter, and serve immediately with the sumac relish.