Lamb Skewers: Combine all ingredients in a bowl. Season and mix well with damp hands. Divide lamb into 4 portions, ensure hand are wet and form the meat around skewers. Place on a tray, cover with cling wrap and refrigerate for 1 hour. Pre-heat barbeque. Using separate skewers, add the peppers and red onions, brush with oil.
Cook for skewers for 4-6 minutes on each side. Turning regularly. Repeat the process for all skewers, until slightly charred, browned and cooked through.
Sumac Onions: Place all ingredients in an airtight container, toss to combine. Season and allow to marinate for at least 10 minutes or up to 48 hours.
Tomato Salad: Whisk together oil, vinegar and sugar. Season to taste, set aside. Add tomatoes, eschallots, capers and basil on a platter, drizzle over dressing and serve.
Squeeze over lemon. Serve on flat bread with sumac onions and tomato salad.
