Remove the sardines from the can, leaving the oil behind. Place in large bowl and mash with a fork.
Add the lemon zest and juice, shallots or onions, capers, parsley, oil, salt and pepper.
Make sandwiches with the sardine mixture. It's nice to toast the bread, if you wish. Great with lettuce and fresh sliced tomatoes. Serve immediately.
You can make the salad up to several hours ahead and refrigerate in an airtight container; or store leftovers the same way for up to a couple days.