Turkey served with tuna sauce certainly isn't a common flavor combo for the American palate, but give it a try. The pairing of flavors truly is tasty. It's traditionally served chilled, but we served the sauce at room temperature over warm turkey. The sauce is delicious over chicken, too.
Place turkey tenderloins in an 8-inch square baking dish; rub with oil. Sprinkle tenderloins evenly with Italian seasoning, salt, and pepper. Pour 1 cup chicken broth into dish. Bake, uncovered, at 350° for 35 to 40 minutes or until a thermometer registers 170°. Let stand 10 minutes.
While turkey stands, place remaining 1/4 cup broth, mayonnaise, and next 5 ingredients in a food processor; process until smooth. Remove turkey from dish; discard broth. Cut tenderloins diagonally into 1-inch-thick medallions. Spoon sauce over sliced turkey, and sprinkle with parsley. Serve warm.
Tonnato (tohn-NAH-toh) means "tuna sauce" in Italian.