Add the olive oil, vinegar, cumin, chili powder, garlic, cinnamon, and salt to a blender bottle or jar with a tight lid. Shake until ingredients are well combined. Set aside.
Combine water and salt in heavy large saucepan over high heat. Add lentils; bring to boil. Cover, reduce heat to medium-low, and simmer until lentils are tender and have absorbed the water completely, about 15 to 20 minutes. Stir in 3 or 4 tablespoons of the dressing.
Heat 2 tablespoons olive oil in large skillet over high heat. Add onion and sauté until dark brown and soft, about 5 minutes. Add chicken and sauté 2 minutes. Add salt, cumin, chili powder, and cinnamon. Sauté until chicken is cooked through, about 3 minutes longer.
Place a serving of lentils on a plate and cover with sliced chicken and dressing. Garnish with chopped parsley.