Heat the vegetable oil in a large heavy-bottomed pot over medium heat.
Add the finely chopped onions and sauté until golden brown, about 10 minutes.
Stir in the minced garlic, grated ginger, and slit green chilies; sauté for an additional 2 minutes until fragrant.
Add the lamb cubes to the pot, browning them on all sides for about 5-7 minutes.
Mix in the chopped tomatoes and cook until they soften, about 3-4 minutes.
Sprinkle in the turmeric powder, garam masala, coriander powder, and cumin powder; stir well to coat the meat evenly with the spices.
Pour in the coconut milk, stirring to combine. Add salt to taste.
Bring the mixture to a gentle simmer, then cover and let cook on low heat for about 1.5 hours, or until the lamb is tender, stirring occasionally.
Adjust seasoning if necessary and garnish with freshly chopped cilantro before serving.
Notes
Serve the lamb curry in a decorative bowl, accompanied by fragrant basmati rice or naan. Garnish with additional cilantro and lime wedges for a burst of freshness.