Cube chicken to 1 to 1½ inch pieces. Add them to a mixing bowl. Make sure there is no excess moisture in your chicken. If you want you may pat dry with a few kitchen tissues.
Add red chilli powder, garam masala, cumin powder, coriander powder, turmeric, salt, lemon juice, oil, ginger garlic paste, yogurt and kasuri methi. Skip the lemon juice if your yogurt is sour.
Mix well. Cover with a cling wrap and refrigerate for minimum of 8 hours and up to 48 hours. If you are in a rush, you may cut down to 3 hours.
Heat oil or ghee in a pot or pan. Add onions and sprinkle 1 teaspoon salt. Saute until deep golden.
Add ginger garlic paste and green chilli. Saute until aromatic, for 40 to 60 seconds.
Reduce the heat to low. Add red chilli powder, coriander powder, garam masala and cumin powder. Stir well quickly.
Pour tomato puree and cook on a medium high heat until the onion tomato masala becomes really thick and begins to leave the sides of the pan. It also turns fragrant. (Check video for consistency)
Pour 2 cups of hot water and cover. Simmer until thick, yet of pouring consistency. (Check video for consistency)
Grill in Oven : While the gravy simmers, thread the chicken to the metal skewers or soaked bamboo skewers and place them in a prepared tray. Bake them in a preheated oven at 460 F or 240 C for 9 to 10 mins. Turn them to the other side with a tong and grill then for another 9 to 10 mins. To char the chicken, broil for 2 to 3 mins or until slightly charred.
Or In a Skillet: Pour 1 tbsp oil to a skillet and heat it well. Place the chicken tikka one by one, spacing them apart. Cook on a medium high heat for 3 mins, turn them to the other side with a tong and cook for another 3 mins, until charred and not essentially fully cooked. Remove to a plate and Cook in batches.
Or In the Air fryer: Thread on skewers and place them in the basket or in the tray. Air fry for 6 mins, at 400 F or 200 C. Turn them with tongs and air fry for another 6 mins. If they dry out, you may baste with marinade and continue for another 2 mins, until slightly charred.
When the tikka masala turns thick, add sugar and the cream (or cashew cream, check notes to make your own). Stir well and cook for a few minutes until thick, creamy and aromatic. (Check video for consistency)
Add the grilled chicken tikka and crushed kasuri methi. (Make sure your gravy has reached a thick gravy consistency/serving consistency, before adding chicken). Stir and cook for 2 to 3 mins until chicken tikka is soft and tender. Taste test and add more salt and sugar if needed.
Turn off and garnish with cream and coriander leaves. Serve chicken tikka masala with Butter Naan, roti, paratha, Basmati rice or Jeera rice.