Melt butter over medium heat. Add onion and cook until tender, about 4 minutes. Add garlic and ginger and cook 1 minute more.
Stir in spices and cook until fragrant, about 2 minutes.
Stir in the tomatoes and heavy cream, simmer 6-8 minutes or until slightly thickened.
Add chicken and simmer 3-4 minutes more or until heated through. Season with kosher salt to taste.
Serve over cauliflower rice and garnish with cilantro if desired.
Notes
Keep leftover keto butter chicken in an airtight container in the refrigerator and use within 4 days.Reheat on the stovetop or in the microwave.Freeze chilled butter chicken in freezer bags for up to 2 months.