Preheat oven to 350°F. Line two cookie sheets with parchment paper or silicone baking mats.

In a large bowl, cream ½ cup (113 g) softened unsalted butter and ⅓ cup (67 g) granulated sugar with a hand or stand mixer until light and fluffy.

Add ½ teaspoon vanilla or almond extract, 1 large egg yolk, and ¼ teaspoon salt; mix until combined.

Gradually add 1 ¼ cups (155 g) all-purpose flour and mix just until the dough comes together. Do not overmix.

Scoop dough into ¾–1 tablespoon portions. Roll each portion between your palms to form a smooth ball and place balls 2 inches apart on the prepared cookie sheets.

Use your thumb, a knuckle, or the back of a ½ teaspoon to press a shallow indent into the center of each cookie.

Spoon jam into the indents, using the ¼ cup jam provided. Fill each indent only to the top so jam does not overflow while baking.

Bake at 350°F for 15–20 minutes, rotating the pans halfway through baking, until the cookies are no longer glossy and the bottoms are light golden.

Let the cookies cool completely on the cookie sheets before removing. Store in an airtight container for up to 3 days or freeze for up to a month.