Combine the lamb cubes with 1 tablespoon of ginger garlic paste and 1/2 teaspoon of salt. Let rest for 15 minutes while prepping other ingredients.

Heat 2 tablespoons of oil in a heavy-bottomed pot over medium-high heat. Add the lamb in batches and sear until browned on all sides. Remove the lamb and set aside.

Add the remaining 1 tablespoon of oil to the same pot over medium heat. Add the sliced onions and cook, stirring frequently, until deeply golden brown.

Stir in the remaining ginger garlic paste and cook for 1 minute until the raw smell disappears. Reduce heat to low, then add turmeric, Kashmiri chili powder, coriander, and cumin. Stir for 30 seconds.

Add the chopped tomatoes and salt. Cook over medium heat, stirring and mashing the tomatoes, until they break down into a thick paste and oil starts to separate at the edges.

Return the browned lamb and any accumulated juices to the pot. Pour in 1 cup of water and bring to a boil. Reduce heat to low, cover with a tight-fitting lid, and simmer for 60 to 75 minutes, stirring occasionally, until the lamb is tender and yields easily to a fork.

Uncover during the last 10 minutes if the gravy is too thin, or add a splash of water if it becomes too thick. Stir in the garam masala, check for doneness, and remove from heat.