Prepare clarified butter; set aside.
Cut pork tenderloin crosswise into 4 slices. Place 1 of the pork pieces, cut side down, between 2 pieces of heavy plastic wrap. Using the flat side of a meat mallet and from the center of pork to the edges, pound meat to 1/4-inch thickness. Remove plastic wrap. Set pork aside.
In food processor bowl or blender container, process or blend macadamia nuts (a portion at a time, if necessary) until chopped. In a small bowl, combine the nuts, salt, and pepper. Lightly brush the surface of each tenderloin with about half of the clarified butter. Sprinkle the nut mixture over each tenderloin, firmly pressing into both sides so the nuts stick to the meat.
In a large skillet, heat the remaining butter over medium-high heat. Cook 2 tenderloin slices in hot butter over medium heat for 6 to 8 minutes or until pork is no longer pink, turning once. (Reduce heat during cooking, if necessary, to prevent overbrowning.) Remove pork from skillet and keep it warm. Repeat with the remaining meat. To serve, transfer tenderloins to warm serving platter. Makes 4 servings.
In a small heavy saucepan, melt butter over low heat without stirring. When the butter is completely melted, slowly pour the clear, oily layer into a custard cup, leaving the milky layer in the pan. The clear liquid is the clarified butter. (You may discard the milky portion or add to cream sauces and soups.) Makes about 3 tablespoons clarified butter.