01 - Preheat the oven to 350°F. Line two baking sheets with parchment paper.
02 - In a large bowl, beat the softened butter and granulated sugar together until light and fluffy, approximately 2-3 minutes.
03 - Mix in the egg yolk and vanilla extract until fully incorporated and smooth.
04 - Add the salt and flour to the mixture. Stir until just combined, being careful not to overmix the dough.
05 - Scoop tablespoon-sized portions of dough and roll each into a smooth ball. Arrange on the prepared baking sheets, leaving approximately 2 inches between each cookie.
06 - Press your thumb or the back of a small spoon into the center of each dough ball to create a deep indentation.
07 - Spoon approximately 1/2 teaspoon of flower jam into each well, being careful not to overfill.
08 - Bake for 12-15 minutes, or until the edges are just beginning to turn golden brown while centers remain slightly soft.
09 - Let the cookies rest on the baking sheets for 5 minutes to firm up, then transfer to a wire rack to cool completely.
10 - Once fully cooled, lightly dust with powdered sugar for an elegant presentation.