Combine the shallot, garlic, parsley, cilantro, lemon zest, lemon juice, salt, pepper and olive oil in a blender and puree until blended.
Gently rinse the scallops, pat dry and remove the tough muscle on the side of each scallop. Sprinkle the scallops with salt and pepper. Heat the butter and the olive oil together in a large non-stick skillet, over medium-high heat. When the butter/oil is really hot, place each scallop in the pan with tongs and let it sit without moving for 2-3 minutes or until just cooked through. Turn over each scallop and cook for another 2-3 minutes. The scallops will develop a nice crust on the outside but remain translucent in the middle. Remove the scallops to a plate and spoon the gremolata sauce over the scallops. Finish with a sprinkle of lemon zest and a squeeze of lemon juice.