Heat oil in a large pan and sauté the chopped onions until golden brown.
Add minced garlic and grated ginger, cooking until fragrant.
Stir in the pureed tomatoes and cook until the oil separates.
Add the mutton pieces and brown them on all sides.
Mix in the curry powder, turmeric, and red chili powder.
Pour in the yogurt and mix well to coat the mutton.
Add salt to taste and enough water to cover the meat.
Cover the pan and simmer on low heat for about 40 minutes.
Check for tenderness and adjust seasoning as needed.
Garnish with fresh coriander leaves before serving.