Marinate the chicken with lemon juice, salt, and turmeric. Let it sit for 15 minutes.
Heat oil in a pan over medium heat. Add cumin seeds and let them sizzle for 30 seconds.
Throw in the chopped onions and sauté until golden brown.
Stir in the ginger-garlic paste and cook until the raw smell disappears.
Add the tomato puree, then mix in coriander, garam masala, red chili, and turmeric powder.
Cook the masala until it thickens and oil starts separating.
Drop in the marinated chicken and cook until it turns white on all sides.
Meanwhile, blanch the spinach in boiling water for 2 minutes, then blend into a smooth puree.
Pour the spinach puree into the pan and let everything simmer for 10 minutes.
Stir in cream or yogurt to make it rich and velvety.
Finish with a tablespoon of butter for that restaurant-style shine.
Garnish with cilantro and a squeeze of lemon before serving.