To a mixing bowl, add yogurt, red chili powder, ginger garlic paste, garam masala, turmeric, kasuri methi, oil, lemon juice & salt.
Mix well and taste test it. Add more salt if required. Add paneer cubes & gently mix well to coat the paneer with the marinade.
Optional - If using onions & bell peppers, dice them to the same size as that of paneer. Separate the layers in the onion. Add them along with bell pepper and marinate gently. Set this aside until the gravy is done.
Heat half of the oil and add the chopped onions. Saute them well until transparent or golden on a medium heat.
Add tomatoes, cashews, sugar and salt. Saute all of these well until the tomatoes turn mushy and soft.
Stir in red chilli powder & garam masala, Saute for another 2 mins, until the masala smells good & aromatic.
Cool this completely and add to a blender. Pour water and blend to a smooth puree.
Heat the rest of the oil in a pan on a low flame. Add ginger garlic paste & saute for 1 to 2 mins, until the raw smell disappears
Pour the onion tomato puree. (Careful as it may splash). At this step, taste test and add more red chilli powder if you want to achieve a brighter color.
Pour water to bring this to a gravy consistency. Cook covered until the gravy turns thick and you see traces of oil on top. Keep stirring in between.
Once the gravy is thick yet of a pouring consistency, crush the kasuri methi in your palms and sprinkle it. (optional). Taste the gravy & add more salt if needed. Rest this aside.
Option 1 - Grill in oven. Preheat the oven to 430 F or 220 C for at least 15 mins. Line a baking tray with foil. Thread paneer, onion & bell peppers alternately on skewers. Place the skewers in the baking tray & grill for 8 to 10 minutes, turning them to the other side after 5 mins. Remove them when golden and crisp.
Option 2 - To make on griddle. Heat a tsp oil in a wide pan on a high flame, coat each paneer piece with the marinade & place on the griddle. Cook on a high flame till the marinade dries up and paneer turns golden. Similarly place the bell peppers and marinated onions and fry until the marinade dries up.
Option 3 - Air fryer. If your air fryer needs preheating, you may preheat it for 5 mins first. Thread paneer, onion, bell pepper on skewers. Air fry the skewers placed in a tray at 390 F or 200 C for 5 mins. Brush them with the marinade and then air fry for another 2 mins. The marinade has to partially dried up. Also adjust the air fryer time as needed.
Transfer grilled paneer tikka along with veggies & onions to the tikka masala gravy.
Pour the cream. Gently mix. Garnish with cream and coriander leaves.
Serve paneer tikka masala with Roti, Butter Naan, Basmati Rice or Jeera rice