Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.

In a large mixing bowl, cream together the butter and sugar using an electric mixer on medium speed for 2-3 minutes.

Add the egg yolks and vanilla extract to the mixture and beat on low speed until combined.

In a separate bowl, whisk together the flour and salt, then gradually add this mixture to the creamed butter.

Cover the dough with plastic wrap and refrigerate for 30 minutes.

Prepare the cinnamon sugar by mixing granulated sugar and cinnamon in a shallow bowl.

Scoop tablespoon-sized balls of dough, roll them in the cinnamon sugar, and place them on the prepared baking sheets.

Create an indent in the center of each ball and fill with apple butter.

Bake for 12-14 minutes until edges are slightly golden.

Allow to cool on baking sheets for 5 minutes before transferring to a wire rack.