I have always shied away from this dish, lacking the necessary tamarind ingredients. Turns out, vinegar is a pretty good substitute, as optimized by Milk Street.
2 lb chicken thighs halved
0.25 cup plus 2 tbs white vinegar
12 garlic cloves
1 inch fresh ginger sliced
2 tbsp paprika
2 tbsp brown sugar
0.25 tsp cloves
2.5 tsp turmeric
2 tsp cumin
1 tsp cayenne
0.25 tsp cinnamon
Blend the quarter cup of vinegar with the garlic cloves, ginger, paprika, sugar, cloves, turmeric, cumin, cayenne, cinnamon, and 1.25 tsp salt and pepper each, plus 3 tbsp water.
Toss with chicken and allow to marinade for 15-20 minutes.
Preheat a large cast iron pot on medium until the oil is shimmering.
Add the chicken and all the marinade, distributing evenly and allowing to brown without stirring for 5-9 minutes.
Stir then add 1/3 cup water and bring to a simmer. Cover and simmer on low for 35-45 minutes.
Mix in the vinegar and cook uncovered until sauce it thick. Serve with naan and rice.