01 - Whisk together Meyer lemon juice, zest, granulated sugar, egg yolks, and salt in a medium saucepan. Add butter cubes. Cook over medium-low heat, whisking continuously for 8–10 minutes until thickened and coating the back of a spoon, ensuring mixture does not boil.
02 - Pour curd through a fine-mesh sieve into a clean bowl. Press plastic wrap directly onto surface to prevent skin formation. Refrigerate for minimum 1 hour until completely set.
03 - Whisk all-purpose flour, almond flour, baking powder, and salt in a medium bowl until thoroughly blended.
04 - Beat softened butter and powdered sugar in large bowl until light and fluffy, approximately 2–3 minutes. Incorporate egg yolk, vanilla extract, and Meyer lemon zest until smooth.
05 - Gradually add dry ingredients, mixing just until combined. Divide dough into two equal portions, flatten into discs, wrap in plastic. Refrigerate for minimum 1 hour.
06 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
07 - Roll one dough disc on lightly floured surface to 1/8-inch thickness. Cut 2-inch rounds. Cut small decorative shape from center of half the rounds to create windows. Repeat with second disc, re-rolling scraps as needed.
08 - Arrange cookies 1 inch apart on prepared sheets. Bake 10–12 minutes until edges are lightly golden. Cool on baking sheet for 2 minutes, then transfer to wire rack to cool completely.
09 - Dust window-cut cookies generously with powdered sugar. Spread 1 teaspoon chilled Meyer lemon curd onto flat side of each solid cookie. Gently press window cookie atop curd, pressing lightly to form sandwich.