Follow these easy steps to create a mouthwatering Chicken Tikka Vindaloo:

1. Marinate the Chicken: In a bowl, combine yogurt, vegetable oil, vinegar, ginger-garlic paste, cumin, coriander, turmeric, red chili powder, garam masala, and salt. Mix well and add chicken pieces. Coat thoroughly, cover, and refrigerate for at least 2 hours or overnight.

2. Prepare the Base: In a large pan, heat some oil over medium heat. Add the chopped onions and sauté until they turn golden brown.

3. Cook the Onions: Stir in the pureed tomatoes and cook for another 5-7 minutes until the oil separates. This enhances the flavors in the base.

4. Add Marinated Chicken: Add the marinated chicken pieces to the pan. Mix thoroughly to incorporate the spices with the onion-tomato mixture.

5. Simmer the Dish: Pour in water to reach your desired consistency. Bring it to a boil, then reduce the heat to low and cover the pan. Let it simmer for 25-30 minutes, stirring occasionally until the chicken is cooked through and tender.

6. Adjust the Spiciness: Taste for seasoning and add slit green chilies if you prefer additional heat. Let it simmer for a few more minutes.

7. Garnish and Serve: Once done, remove from heat and garnish with fresh cilantro before serving.

8. Serve Hot: Pair with naan, rice, or any bread of your choice.