This is Lorna Sass’s recipe from the original Cooking Under Pressure. The only change I’ve made to her recipe is to brown the lamb. It adds flavor and improves the color.
2 pounds lamb shoulder, cut into 2-inch cubes
Salt and black pepper
2 tbl olive oil
2 medium onions, thinly sliced
3 cloves garlic, minced
2 tbl tomato paste
¼ cup red wine vinegar
½ cup water
2 tsp sweet paprika
1 ½ tsp dry thyme
1 bay leaf
1 14-ounce can diced tomatoes plus their juice
1 large sweet red pepper, cut in thin slices
1 large sweet green pepper or poblano, cut in thin slices
Season the cubed lamb with salt and pepper. Brown the meat in olive oil in a sauté pan or in the bottom of the pressure cooker.
In the fat in the bottom of the pan, sauté the onion and garlic until soft, about 3 minutes. Stir in the tomato paste and cook an additional minute. Stir in the vinegar and water, paprika, thyme and bay leaf. Add the lamb. Pour the tomatoes on top. Do not stir.
Cover the pressure cooker and bring up to full pressure for 12 minutes. Let the pressure drop naturally, 7 to 10 minutes. Add the sliced peppers and simmer uncovered until they are crispy tender, about 5 more minutes. Taste the lamb for tenderness and also adjust the seasonings. If the meat is tender but you want more intense flavor, set the meat aside and quickly reduce the sauce. This is great the next day after flavors have had a chance to meld, and you can easily lift the congealed fat off the top.