Alfajores

Instructions

1. Prepare the dry ingredients
   In a medium bowl, whisk together the cornstarch, all-purpose flour, baking powder, baking soda, and salt until well combined. Set aside.
2. Mix the wet ingredients
   In a large bowl, beat the softened butter and sugar with an electric mixer until light and fluffy, about 3 minutes. Add the egg yolks one at a time, beating well after each addition. Stir in the vanilla extract and lemon zest (if using).
3. Form the dough
   Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. The dough will be soft. Form the dough into a ball, wrap in plastic wrap, and refrigerate for at least 1 hour or up to overnight.
4. Prepare for baking
   Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper. On a lightly floured surface, roll out the chilled dough to about 1/4 inch thickness. Using a 2-inch round cookie cutter, cut out circles and place them on the prepared baking sheets, spacing them about 1 inch apart.
5. Bake the cookies
   Bake in the preheated oven for 10-12 minutes, or until the edges are just barely golden. The cookies should remain pale. Allow them to cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely.
6. Assemble the alfajores
   Once the cookies are completely cooled, spread about 1-2 teaspoons of dulce de leche on the flat side of one cookie. Place another cookie on top, flat side down, to make a sandwich. Press gently to spread the filling to the edges.
7. Finish the cookies
   If desired, roll the edges of the filled cookies in shredded coconut to coat the exposed dulce de leche. Dust the tops of the cookies with powdered sugar. Store in an airtight container at room temperature for up to 3 days, or refrigerate for up to a week.