Preheat the oven to 350 degrees. Prepare two large baking sheets by lining with parchment paper, greasing or spraying with cooking spray.
Stir together flour, baking soda, baking powder and salt in a medium bowl. Set aside.
2 ¼ cups all-purpose flour, scant ½ tsp. baking soda, ¼ teaspoon baking powder, ¼ teaspoon salt
In a large bowl, combine the butter, sugar and egg yolk. Beat at medium speed with an electric mixer until fluffy and well blended. Add the cream cheese, vanilla and lemon zest beating until evenly incorporated.
1 cup butter, 1 cup powdered sugar, 1 large egg yolk, 3 ounces cream cheese, 1 ½ teaspoon vanilla, 1 teaspoon finely grated lemon zest
On low speed, beat in the flour mixture until well blended. Let stand for 5 to 10 minutes or until dough firms up slightly.
Shape portions of the dough into balls approximately 1-inch in diameter. (Place the dough in the palm of your hand and cup your other hand over the top. Roll the dough between your cupped hands to form a smooth little ball.)
Dip the tops of the balls into the chopped nuts, if using.
⅔ cup finely chopped nuts
Place the balls, nut side up, on the baking sheets, about 1 ½ inches apart.
Using your thumb, press a deep well into the center of each ball.
Place about ¼ teaspoon jam in each indentation.
12 teaspoons seedless jam
Bake the cookies, one sheet at a time, in the upper third of the oven for 9 to 12 minutes or until the cookies are just barely brown at the edges. Reverse the baking sheet halfway through baking to ensure even browning.
Transfer the baking sheet to a wire rack and let stand until cookies firm up slightly, about 2 to 3 minutes.
Remove the cookies from the pan and place them on the wire rack to cool completely.
Store in an airtight container for up to two weeks or freeze for up to a month.
Notes
For best results, use the fluff, scoop, and level method explained in the post when measuring flour.
Choose seedless, smooth jam and fill each indentation with no more than ¼ teaspoon to prevent overflow.
Store cookies in an airtight container at room temperature for up to 2 weeks, or freeze for up to 1 month.