Heat oil in a large skillet over medium heat. Add onions and cook until they are soft and translucent, about 5 minutes.

Add garlic and ginger to the skillet and cook for another minute until fragrant.

Stir in garam masala, cumin, coriander, turmeric, and cayenne pepper. Cook for 2 minutes, stirring frequently to prevent spices from burning.

Pour in the crushed tomatoes and bring the mixture to a simmer. Let it cook for about 10 minutes, stirring occasionally.

Reduce heat to low and stir in the heavy cream. Simmer for an additional 10-15 minutes, until the sauce thickens to your desired consistency.

Season with salt to taste. Garnish with chopped cilantro before serving.