Remove the outer leaves of the artichokes. Cut off the tips of the leaves and remove the fuzzy interior. Then cut into slices. Squeeze the juice of a lemon into a bowl and fill with water. Place artichokes in the water as you trim them, so that they don't turn brown. Trim the fennel and reserve the fronds. Cut into thin slices using a mandolin or other slicer. In a salad bowl, mix the vegetables with a tbsp of capers. Add the dressing made with orange juice, salt and 1/4 cup olive oil. Garnish with the fennel fronds and freshly ground pepper. Serve immediately and toss in front of the guests.