Open the instant pot and add salt, tamarind paste and spices to the instant pot (which has the cooked peas(matar), onions etc), stir well and press saute. Let the mixture simmer for about 3 to 4 minutes (stir in between).
Once the curry is simmered enough, press 'cancel' to stop the saute function.
Carefully transfer the fried potatoes to the instant pot one by one.
Also, add few tablespoons of oil (about 4 tablespoons) from the pan used to fry the potatoes to the instant pot carefully (the oil could be very hot so its a good idea to transfer the oil to a bowl first and then add this to the instant pot). You may also add a couple of spoons of heavy cream, a teaspoon of kasoori methi (dried fenugreek leaves) etc at this point, if you wish to make this dish even more creamy & flavorful.
Gently mix everything, spoon some of the gravy over the potatoes and keep the instant pot closed at least for about 10 to 15 minutes so it will further cook in the residue heat and the gravy will get absorbed into the dum aloo or potatoes.
Enjoy the delicious dum aloo matar curry or fried potatoes and peas curry with Indian breads like chapathi, poori, naan bread etc or with rice as you like.