Whisk the flour, baking powder, and salt in a mixing bowl. In a separate bowl, beat the milk, egg, and 2 tablespoons melted butter until smooth. Pour the wet mixture into the dry ingredients and stir just until combined. Let the batter rest for 5 minutes.
Heat a nonstick skillet over medium heat and brush lightly with butter. Drop teaspoon-sized portions of batter into the skillet. Cook for 1 minute until bubbles form on the surface, then flip and cook for 30 seconds more. Transfer the blini to a plate and repeat with the remaining batter.
Stir the crème fraîche with the lemon zest and lemon juice in a small bowl until blended.
Arrange the blini on a serving platter. Top each with a small piece of smoked salmon, a dollop of lemon crème fraîche, and a small amount of caviar. Finish with a dill sprig on each blini.