In a large mixing bowl, combine the chicken with garlic, ginger, apple cider vinegar, tamarind paste, and brown sugar. Mix well until the chicken is thoroughly coated. Let it marinate for at least 30 minutes, but ideally a few hours for maximum flavor.

Tip: For even more depth, marinate overnight in the fridge.

Heat the vegetable oil in a deep skillet or Dutch oven over medium heat. Add the chopped onions and sauté until golden and fragrant, about 5-7 minutes. Stir in green chilies, followed by the spices: cumin, coriander, turmeric, and paprika.

Tip: Toasting the spices will enhance their aroma and flavor.

Add the marinated chicken to the skillet, stirring well to coat it in the spice mixture. Sear for about 5 minutes until the chicken is browned. Pour in the diced tomatoes and season with salt.

Tip: Scrape the bottom of the pan to capture any flavorful bits stuck on the surface.

Reduce the heat to low and cover the skillet. Allow the chicken to simmer for 30 minutes, stirring occasionally. The sauce should thicken, enveloping the chicken beautifully.

Tip: If you want a thinner sauce, add a splash of water or chicken broth while cooking.