Put the chillies in a small blender or food processor and process until ground.
Put the pepper and coriander, pastes, and ground chillies into a large bowl, season with salt, and mix well.
Spread the paste evenly over the meat, put it into a large, shallow dish, cover and allow to marinate in the refrigerator for 1 - 1 1/2 hours.
Prepare a tandoor or charcoal grill for moderate heat, or alternatively preheat the grill (broiler) to medium. Lightly brush a wire mesh or grill rack with oil.
Place the marinated meat on the mesh or rack and cook over a moderately hot charcoal grill or under the hot grill for about 30 minutes, basting the meat with oil, until the meat is cooked.
Serve with sliced onions and a little lemon juice sprinkled over the top.