1. In a stand mixer fitted with the paddle attachment, cream together the softened butter, granulated sugar, and ground cinnamon on medium speed until light and fluffy, about 3–4 minutes.

2. Add the egg yolk and vanilla extract, mixing until fully incorporated.

3. In a separate bowl, whisk together the all-purpose flour, almond flour, and salt.

4. Gradually add the dry ingredients to the butter mixture, mixing just until combined.

5. Divide the dough into two equal portions, flatten into disks, wrap in plastic wrap, and refrigerate for at least 1 hour.

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

7. On a lightly floured surface, roll out one disk of dough to about 1/4-inch thickness. Using a 2-inch round cookie cutter, cut out cookies. For half of the cookies, use a smaller cutter to remove the center, creating a window.

8. Place the cookies on the prepared baking sheets and refrigerate for 15 minutes to prevent spreading.

9. Bake for 10–12 minutes, or until the edges are lightly golden. Allow to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.

10. Once cooled, dust the top (window) cookies with confectioners’ sugar. Spread about 1 teaspoon of dulce de leche onto the bottom cookies, then sandwich with the sugared tops.