Grind the onion, garlic and ginger to a paste. Clean the chicken and make 3-4 shallow cuts. In a large plate, beat the yogurt. Into this, add the coriander and cumin powder, the onion garlic mixture, salt, vinegar and lemon juice.
Mix to form a thin paste. Apply into the chicken. Allow the chicken to marinate for 4 hours, covered in the refrigerator. Grill on a barbecue. I''ve tried to bake this in the oven and it tastes pretty good, though not as good as the grill. If baking, bake at 400 deg F for 20-25 minutes, and then broil for 5 minutes until brown.