Season the loin of veal with pepper. Heat the oil in a large pan and sear the veal briefly on all sides.Wrap in plastic wrap and then in aluminum foil, seal well. Bring a large wide pan of water to a simmer, add the veal, cover and poach until cooked through, about 30 minutes. Cool in the foil.
In a blender, puree the creme fraiche, vegetable broth, cream, tuna and anchovies, season with salt and pepper.
Rinse the arugula and remove the stems. Arrange on plates. Thinly slice the veal and place on the arugula. Pour the sauce over and garnish with capers.