Mix in a large bowl the onions along with the lemon juice, paprika and the lemon zest. Add the chicken thighs, mix well and keep aside for 30 minutes.
Prepare the marinade by adding in a medium bowl the yoghurt and mixing with garlic, ginger, cumin, garam masala, turmeric, cayenne chili powder, salt and pepper. Add the marinade on the chicken thighs, toss well and cover with plastic film. Refrigerate for an hour or even overnight.
Turn the oven grill on, max Degrees C, rack towards the top.
Take a large rectangular non-stick oven dish and lightly brush with the oil. Pick the chicken thighs while lightly removing the excess marinade and add in the oven dish. Grill for 15-18 minutes, tossing the chicken halfway through aiming to give a nice char to the chicken.
Serve in a dish along with Basmati Rice and sprinkle on top the coriander.