Delicate thumbprint cookies filled with jewel-toned jam are a charming, family-favorite holiday treat. These buttery, tender cookies add elegance to any celebration cookie platter.
Preheat oven to 350°F (175°C) and line two baking sheets with parchment paper.
Cream the butter and sugar together using a mixer on medium speed until light and fluffy, about 2–3 minutes.
Add egg yolks and vanilla extract; mix until fully incorporated, scraping the bowl as needed.
Gradually add the flour and salt on low speed, mixing just until a soft dough forms. Do not overmix.
Scoop 1 tablespoon of dough per cookie, roll into balls, and place on prepared sheets. Press a deep indentation in the center of each ball with your thumb.
Fill each indentation with 1 teaspoon of fruit jam, taking care not to overflow.
Bake for 12–15 minutes, rotating halfway through, until the edges are golden and the cookies are set.
Cool cookies on the baking sheets for 5 minutes before transferring to a wire rack.