In the same pan, add cooking oil and chopped onions. Cook the onions for 2-3 minutes, or until translucent.
Add the tomatoes, raw cashews, minced garlic, and diced tomatoes. Mix well
Then, add the water, vinegar, ginger-garlic paste, chili powder, turmeric, cumin, sugar, and half of the garam masala and ground coriander. Mix well and let the mixture simmer over medium-low heat for 20 minutes.
After at least 20 minutes, the cashews and tomatoes should have softened. Carefully add the mixture to a heat-safe high-powdered blender and blend until smooth (or use an immersion blender).
Pour the sauce back into the skillet. Add the butter, coconut cream, remaining garam masala, and ground coriander to the skillet. Mix well and simmer over medium-low heat for 5-7 minutes. Mix in fenugreek leaves, optional.
Stir and taste, adjust the flavor as needed. Add more garam masala and ground coriander, as desired.
Garnish with chopped cilantro and coconut cream. Enjoy!