Remove all fat and tendons from the tenderloin. Place in the freezer to firm, 15 to 20 minutes.
2.
Combine remaining ingredients in a non-aluminum pot. Bring to a boil, reduce heat, and simmer for 10 minutes. Cool and strain. Discard solids. Reserve marinade.
3.
With sharp knife or slicing machine, cut the tenderloin into paper thin slices. Arrange the tenderloin slices on a bed of lettuce. Place a small mound of finely chopped onions and capers in the center. Garnish with orange wedges or sliced lemon, if desired.
