Drizzle 1 tablespoon vinegar over 10-12 Kashmiri dry red chilies and set them aside for 20 minutes.
Dry roast 2 tablespoon whole coriander seeds, 3-4 cloves, 1-inch piece of whole cinnamon, 2-3 green cardamoms, 8-10 whole peppercorns, 1 teaspoon cumin seeds, and 1 teaspoon mustard seeds in a skillet over medium heat until fragrant and slightly browned.
Add the chilies and roasted spices to a blender along with a 1-inch piece of ginger (chopped), 6-8 cloves of peeled garlic, 1 and ½ tablespoon tamarind paste, and ½ cup water and make a smooth vindaloo paste.
Heat 4 tablespoon vegetable oil in a pressure cooker over high heat. When the oil is hot, add 1 cup chopped onion and fry till golden brown (8-10 minutes). Keep stirring frequently.
Add 1 lb (500 g) potato cubes and fry on high heat for 3- 4 minutes.
Add ½ cup tomato puree (or 2 tablespoon tomato paste) and the vindaloo paste that we made earlier.
Now add salt to taste, ½ teaspoon turmeric powder, and 2 cups of water to the cooker.
Close the lid of the cooker and pressure cook for one whistle on high heat and then set the heat to low. Cook for 3-4 minutes on low heat and then remove the cooker from heat. Let the pressure release naturally for 10 minutes. Release the remaining pressure and open the lid of the cooker. Add ¼ teaspoon sugar and cook for another minute.
Serve hot with steamed rice or chapati.
If you are prepping ahead of time, cut the potatoes and add them to a bowl of water until you use it, otherwise, they will turn black because of oxidation.I will suggest you use the store-bought tomato puree for the best taste.You can increase or decrease the spice level according to your heat preference.I have used Kashmiri dry red chilies which gives this curry a fiery red color but they are not as spicy.Instant Pot DirectionsMake the vindaloo paste as mentioned above and set aside.Press SAUTE button of the instant pot. When it says hot, add 4 tablespoon vegetable oil. When the oil is hot, add onion and fry till golden brown (8-10 minutes). Keep stirring frequently.Add potato cubes and fry for 3- 4 minutes. Add tomato puree (or 2 tablespoon tomato paste) and the vindaloo paste that we made earlier.Now add salt to taste, turmeric powder, and 1 and ½ cups of water and stir gently.Close the lid of the pot. Set the valve to the sealing position. Press PRESSURE COOK and set the timer to 6 minutes on high pressure. Once the timer goes off, let the pressure release naturally for 10 minutes.Release the remaining pressure manually and open the lid of the pot.