|Soak wooden skewers, if using, for an hour in water to cover so they don't burn when cooked.|
Place the chicken cubes in a shallow dish and pour lemon juice over chicken. Add onion powder, salt, pepper, and cinnamon; mix well, cover, and refrigerate for at least 1 hour.
Remove from the refrigerator one hour before cooking and let sit at room temperature.
Thread the chicken onto skewers with 4 to 5 pieces of chicken per skewer, alternating with vegetables, if desired. Repeat until each skewer is threaded.
Heat grill or broiler, brush chicken with melted butter, and cook for about 10-12 minutes, turning to brush with butter. Cook on all sides. Brush again with melted butter and serve hot.