Dredge the lamb meat in flour to lightly coat all sides.

Season the floured lamb with salt and pepper to taste.

Heat shortening in a Dutch oven over medium-high heat.

Add the lamb to the Dutch oven and cook, stirring occasionally, until browned on all sides.

Add chopped onion to the pot with the lamb and cook, stirring frequently, for about 1 minute until slightly softened.

Pour in enough hot water to cover the lamb and onions completely.

Bring the mixture to a simmer, then reduce the heat to low, cover the Dutch oven, and simmer gently for 1 hour and 30 minutes, or until the lamb is tender.

Add the carrots and potatoes to the stew and stir to combine.

Continue cooking for 30 more minutes, or until the carrots and potatoes are tender.

Add the peeled and diced tomatoes to the stew and stir well.

Cook for an additional 10 minutes, allowing the tomatoes to soften and release their flavors into the stew.

If desired, thicken the liquid by mixing a small amount of cornstarch with cold water and stirring it into the stew. Simmer until the stew reaches your desired consistency.