BBQ sauce:
Place tomato puree, 1 pint water, Worcestershire sauce, 2 cups yellow onions, 4 teaspoons fresh garlic, brown sugar, chili powder, black pepper, balsamic vinegar, and spicy brown mustard in a medium size pan. Bring to a boil, then simmer for 30 minutes. Remove from the heat and puree sauce.
Caramelized onions:
In a skillet add 1/2 tablespoon olive oil. Sauté 4 cups of red onions with the thyme until golden. Add balsamic vinegar. Reduce liquid then remove from heat. Onions should be cooked but firm.
Spiced chicken:
Blend together: 1/4 teaspoon olive oil, cumin, paprika, cayenne, coriander, 2 teaspoons fresh garlic, 1/2 teaspoon salt, and lemon juice. Marinate with the chicken at least a half hour before cooking. Place chicken on a prepared sheet pan and cook at 350 degrees until internal temperature reaches 165 degrees.
Procedure for flat bread:
Spread 2 tablespoons of homemade barbecue sauce onto flatbread. Top with caramelized onions, diced spiced chicken, and cheese. Place on sheet pan and bake at 375 degrees for 5-7 minutes. Remove from the oven, add the arugula, cut into six pieces and serve.