01 - Preheat oven to 350°F and line two baking sheets with parchment paper.
02 - In a large bowl, cream softened butter and granulated sugar until light and fluffy, approximately 2-3 minutes.
03 - Beat in egg yolk and vanilla extract until fully incorporated into the mixture.
04 - Add salt and flour, mixing until just combined. Avoid overmixing to prevent tough cookies.
05 - Scoop tablespoon-sized portions and roll into balls. Place on prepared baking sheets, spacing 2 inches apart.
06 - Press thumb or back of small spoon into center of each dough ball to form a well.
07 - Spoon approximately 1/2 teaspoon flower jam into each indentation.
08 - Bake 12-15 minutes until edges are just turning golden brown.
09 - Let cookies rest on baking sheets 5 minutes, then transfer to wire rack to cool fully.
10 - Dust cooled cookies lightly with powdered sugar if desired.