Cucumber wash, clean, lengthwise halve, core and very finely dice. Wash lime thoroughly, grate peel finely. Halve lime, squeeze juice. Wash the dill, shake dry, put some flags aside for garnishing, cut the remaining dill finely.
Mix cream cheese, sour cream, lime juice and zest. Season with salt and pepper. Stir in dill and cucumber. Cut salmon into fine strips. Layer cream cheese cream and salmon in glasses. Garnish with one teaspoon each of trout caviar and dill flags