Preheat oven to 350°F (177°C). Prepare a baking sheet lined with parchment paper.
In an electric mixer fitted with the paddle attachment, cream butter and sugar together on medium-high speed until pale and fluffy, about 3 minutes. Beat in the egg yolks one at a time, then add the almond extract and salt. With the mixer on low, add the flour in three batches. Continue to mix until the dough comes together into a ball.
Roll the dough into 1-inch balls and place them 2 to 3 inches apart on the prepared baking sheet. With your finger or the back of a spoon, flatten the cookie slightly and create an indentation in the center of the cookie. Be careful not to press all the way through the cookie, but leave a small hollow for the jam. If the dough is too soft, refrigerate for 5 minutes.
Bake cookies for 10 minutes or until just golden brown on the bottom. Remove baking sheet from the oven. If the hollows have spread a little, use the back of a spoon to redefine them. Spoon about ½ teaspoon jam into each hollow. Bake for another 4 to 6 minutes, or until jam melts slightly and the cookies are golden brown around the edges.
Transfer to a wire rack and let cool completely. Store in an airtight container for up to 2 days.