In a medium skillet, heat vegetable oil or ghee over medium heat. Add chopped onion, minced garlic, and freshly grated ginger. Sauté for 5 minutes until onion is translucent.

Stir in garam masala, ground cumin, ground coriander, turmeric, smoked paprika, salt, and cayenne pepper. Cook for 2 minutes, stirring until spices release their aromas.

Add chicken thighs to the skillet and sear for about 5 minutes until lightly browned. This step locks in moisture.

Transfer chicken and spice mixture to your slow cooker, scraping in any remaining juices from the skillet.

Pour in crushed tomatoes, coconut milk, and tomato paste. Stir to combine all ingredients well.

Cover slow cooker and set to cook on low for 6-8 hours or on high for 3-4 hours.

Once cooking is done, stir in freshly squeezed lemon juice and adjust seasoning if needed.

Ladle the masala into bowls, garnish with cilantro, and serve hot with basmati rice or naan.