Heat oil in a large frying pan over medium-high heat.
Add onions. Saute, stirring occasionally, for about 2-3 minutes or until soft and translucent.
Add garlic and ginger. Saute, stirring, for about 2 minutes or until fragrant.
Add ground cumin, garam masala and red chili powder. Saute, stirring, for about a minute or until aromatic.
Add butter and lemon juice. Stir to combine.
Add tomato paste. Saute, stirring, for about 1-2 minutes.
Stir in cream. Simmer for about 4-5 minutes.
Add cooked meatballs. Toss.
Garnish with coriander (cilantro) leaves.
Serve with your favorite - naan, rice, pasta or garlic bread.