01 - Preheat oven to 350°F and line two baking sheets with parchment paper.
02 - In a large bowl, cream together softened butter and granulated sugar until light and fluffy.
03 - Beat in egg yolk and vanilla extract until fully incorporated.
04 - Add salt and flour, mixing until just combined. Avoid overmixing.
05 - Scoop tablespoon-sized portions, roll into balls, and 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 - Fill each indentation with 1/2 teaspoon of flower jam.
08 - Bake for 12-15 minutes until edges just begin turning golden.
09 - Let cookies cool on baking sheets for 5 minutes before transferring to wire rack. Dust with powdered sugar once cooled if desired.