I have made this with chicken as well.
To serve four.
5 to 10 large garlic cloves, peeled
1 2-inch piece ginger, peeled and coarsely chopped
2 tbsp cider vinegar
½ tsp ground turmeric
1 tsp ground cumin
1 tbsp Indian red chili powder or red pepper flakes
1 tbsp Kashmiri red chili powder or Hungarian hot paprika
2 tsp kosher salt
2 lbs pork shoulder, trimmed of excess fat and cut into 1 1/2-inch pieces
1 inchwide ball of tamarind pulp
¼ cup olive oil or vegetable oil
1 3-inch cinnamon stick
4 green cardamom pods
1 tsp black mustard seeds, coarsely crushed (see note)
1 cup onion, finely chopped
1 large red bell pepper, cut into 1 1/2-inch pieces
Cooked rice for serving
In a food processor or blender, mince garlic and ginger. Add vinegar, turmeric, cumin, chili powders and salt and blend well. Transfer to a large bowl, add pork and turn to coat well. Cover and set aside at room temperature for one hour.
Place tamarind in a bowl with one cup hot water. When cool enough to handle, crush tamarind with fingers to extract pulp clinging to fibers. Add another cup of hot water and mix well. Strain into a clean bowl, discarding fibrous residue.
In a large sauté pan, combine oil, cinnamon, cloves, cardamom and mustard seeds. Fry over medium-high heat until sizzling and aromatic, about 4 minutes. Add onion and cook, stirring often, until lightly browned, about 5 minutes. Add pork and cook, turning until lightly browned, about 6 minutes.
Add tamarind juice and bring to a boil. Reduce heat to medium-low, cover, and cook until pork is tender, about 1 1/2 hours. Add bell pepper and cook 7 minutes. Serve with rice.