How to Make It
Heat oven to 350° F. Spread the almonds on a rimmed baking sheet and toast until fragrant, 6 to 8 minutes. Let cool.
In a food processor, process the almonds and ¼ cup of the brown sugar until the almonds are finely ground.
In a medium bowl, whisk together the flour, baking powder, salt, and cinnamon.
In a large bowl, using an electric mixer, beat the butter and the remaining ¼ cup brown sugar on medium-high until fluffy, 2 to 3 minutes. Beat in the egg and vanilla, scraping down sides of bowl as needed. Reduce speed to low and gradually add the almond mixture, then the flour mixture, mixing until just combined (do not overmix).
Divide the dough in half, shape into two disks, wrap in plastic wrap, and refrigerate until firm, at least 3 hours.
Heat oven to 350° F with racks in upper and lower thirds. Working with one piece at a time, on a lightly-floured piece of parchment, roll out dough to an ⅛-inch thickness. Using a lightly floured egg-shaped cookie cutter, cut the dough into egg shapes. Remove scraps, reroll on a separate piece of floured parchment, and repeat. Transfer parchment and cookies to a baking sheet.
Using a 1-inch bottle cap, cut out circles in from half of the cookies (these are the tops). If the dough is too soft to make a clean cut, freeze until firm.
Bake, rotating the sheets 180° and top to bottom, halfway through, until the edges are golden, 10 to 12 minutes. Cool slightly on the sheets, and transfer to wire racks to cool.
Dust top cookies with the confectioners’ sugar. Spread ½ tablespoon lemon curd on the remaining cookies and top with the sugared cookies. Store in an airtight container at room temperature for up to 5 days.