Heat oil in a large skillet over medium-high heat. Season scallops with salt and pepper and cook until deep golden brown on 1 side, about 4 minutes. Turn scallops and add butter and tarragon to pan. Continue cooking, spooning butter over scallops often, until scallops are cooked through and butter is brown and smells nutty, about 4 minutes longer. Add lemon juice. Serve scallops with brown butter pan sauce.