In blender, puree chopped onion and garlic with garam masala, 1/2 cup of yogurt, 1/4 cup of vinegar, 1/2teaspoon salt and 1/4 teaspoon pepper.
Transfer to medium bowl and add chicken.
Let marinate in refrigerator for at least 2 hours.
Heat 1 tablespoon of oil in a large nonstick skillet over medium heat. Cook the chicken until browned and cooked fully, Let chicken rest for at least 5 minutes before slicing.
In a large bowl, whisk the remaining yogurt, vinegar and oil, salt, pepper with 1 tablespoon water. Add the lettuce, chickpeas, and sliced onion and toss to combine.
Place chicken, avocado and cherry tomatoes on top