Put grated potatoes and onion into a bowl. Add egg, flour, salt, pepper and herbs. Mix well.
Fill a skillet with 1/4 in. (0.5 cm) of oil. Heat over medium-high heat until oil is quite hot.
Using a large spoon, carefully drop a large dollop of potato batter into the skillet and use a lifter to flatten it out into a roughly 3-in. (8-cm) diameter circle. You will need to make eight latkes in total. Try to keep them the same size for even cooking time and presentation.
Fry them to a golden brown on both sides (this should take three to four minutes per side). Remove latkes and pat them dry with paper towels; keep warm.
Combine light cream cheese, lemon juice and lemon rind. Add salt and pepper to taste.
Spread cream-cheese mixture on all eight latkes. On four of them, place a thin slice of smoked salmon and a few sprigs of arugula or other greens, and top with the second potato pancake. Garnish with leftover parsley.