First make the sauce: In a dutch oven or a skillet add ground turmeric and tomato paste to 2 ounces of fried onions and saute for 2 minutes over medium low heat until aromatic. Add 1 ½ cups of water, kosher salt, black pepper, and the optional ground saffron. Bring the sauce to a boil. Turn the heat off, transfer to a bowl and set aside.
On a cutting board, butterfly the cubed beef (please see the illustrated instructions). Use a meat tenderizer to pound and flatten the butterflied beef pieces, first on one side, then the other until about ⅛ inch thick. Set aside.
In a medium Dutch oven or a heavy stockpot with a tight lid, arrange ⅓ of the sliced onion rings in the bottom.
Layer the pounded meat to cover the onion rings, and sprinkle the top with ½ tsp Meat Spice Blend (II).
Layer the top with ½ of the remaining onion slices, the potato slices, the sliced carrots and then top it all with the rest of the onion slices.
Pour the prepared sauce over all the layered ingredients in the pot. Bring the sauce to a boil over medium heat. Reduce the heat to between low and medium low. Cover the pot and simmer for 1 ½ to 2 hours until the meat reaches the desired tenderness and the sauce is reduced. If there is too much liquid left in the pot, keep cooking with the lid off for a few more minutes until the sauce is reduced.
Serve Tas Kabob with flat breads such as sangak, lavash, or pita bread and a side of Sabzi Khordan (fresh herbs), or torshi (pickled vegetables). Alternatively, you may serve it on a bed of rice, cooked Kateh style (Persian quick rice); try sprinkling some sumac on top for a tangy flavor.
Notes
You may use lamb instead of beef in this recipe
Recipe by Persian Mama at https://persianmama.com/tas-kabob/