Heat a small skillet over medium heat. Add the dried Kashmiri red chilies, cumin seeds, coriander seeds, peppercorns, cloves, and cinnamon stick. Dry roast for 1 to 2 minutes until aromatic, stirring constantly to prevent burning.

Transfer the roasted spices to a spice grinder or blender. Add the garlic, ginger, vinegar, and 1 teaspoon of salt. Blend until a smooth paste forms, adding a tiny splash of water if needed to help it move.

Place the chicken pieces in a bowl and coat them thoroughly with the vindaloo paste. Cover and let marinate for at least 60 minutes at room temperature or in the refrigerator.

Heat the cooking oil in a heavy-bottomed pan over medium heat. Add the sliced onions and cook, stirring frequently, until they turn golden brown at the edges.

Add the marinated chicken and turmeric powder to the pan. Sauté for 5 to 7 minutes until the chicken pieces lose their raw pink exterior.

Pour in 1 cup of water and bring to a gentle simmer. Cover the pan and cook on medium-low heat for 20 to 25 minutes, stirring occasionally, until the chicken is tender, cooked through, and reaches an internal temperature of 74°C / 165°F at the thickest piece.

Uncover the pan for the last few minutes if the sauce is too thin, allowing it to reduce to a thick coating consistency. Adjust salt if needed, then serve hot.