In a large bowl, combine yogurt, lemon juice, ground cumin, cayenne pepper, ground coriander, ground turmeric, garam masala, salt, and pepper. Mix well to create a flavorful marinade. Add chicken thighs or breasts, ensuring they are completely coated. Cover and refrigerate for at least 1 hour (or overnight for best results).

Heat 2 tablespoons of butter in a large skillet over medium heat. Once melted, add finely chopped onions and sauté for about 5 to 7 minutes until golden brown.

Stir in minced garlic and grated ginger with the sautéed onions, cooking for an additional 1 to 2 minutes until fragrant.

Carefully introduce the marinated chicken to the skillet. Allow to brown on all sides for about 8 to 10 minutes, stirring occasionally.

Pour in crushed tomatoes, stirring to incorporate. Bring to a gentle simmer and cook for about 15 minutes until the sauce thickens.

Reduce heat to low and stir in heavy cream or coconut milk. Let it simmer for an additional 5 to 10 minutes until the sauce is velvety.

Taste and adjust flavors with additional salt, pepper, or cayenne if desired. Garnish with freshly chopped cilantro.

Plate your Indian spiced butter chicken hot and serve with fluffy basmati rice or warm naan.