Cucumbersandwiches with smoked salmon encourage snacking.
Make tartare: In a small bowl, combine salmon, onion, cilantro, jalapeno, and zest. Season with salt and pepper.
Using a paring knife or vegetable peeler, remove skin on two opposite sides of cucumber. Trim the ends, and cut cucumber crosswise into 48 slices, 1/4 inch thick. Place slices on paper towels to dry.
Using a butter knife or a small offset spatula, spread about 1/2 teaspoon of creme fraiche on half of the cucumber slices, and then top with a teaspoon of tartare. Place remaining cucumber slices on top, followed by a small dollop of creme fraiche and a piece of lime. Serve immediately, or chill, covered with plastic wrap, up to 1 hour.