01 - Preheat the oven to 350°F. Line two baking sheets with parchment paper and set aside.
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, spacing them approximately 2 inches apart.
06 - Using your thumb or the back of a small spoon, press down gently in the center of each dough ball to create a deep well.
07 - Spoon approximately 1/2 teaspoon of flower jam into each indentation, being careful not to overfill.
08 - Bake for 12-15 minutes, or until the edges begin to turn lightly golden.
09 - Let the cookies rest on the baking sheets for 5 minutes before transferring to a wire rack. Once completely cooled, optionally dust with powdered sugar.