Line a cookie sheet with a silicone mat.

In a food processor, add the powdered sugar and almond flour and pulse until fully combined and rid of lumps. Sift the dry ingredients into a large bowl.

Whisk the poppy seeds into the dry ingredients.

Prepare the french meringue by beating the egg whites on low speed until frothy. Slowly add the granulated sugar and beat until stiff peaks form.

Gently fold the french meringue into the dry ingredients until fully combined. It should draw a figure 8 without breaking.

Transfer the batter to a piping bag and pipe 1-inch disks onto the prepared cookie sheet.

Tap the cookie sheet onto the counter 3 or 4 times to bring air bubbles to the surface. Puncture any remaining bubbles with a toothpick.

Let the macarons rest for an hour until a dry layer forms on top.

Preheat the oven to 280 degrees F.

Bake the macarons for 15 minutes, rotating the cookie sheet every 5 minutes.

Allow the macarons to cool completely and match each to another of the same size.

In a medium heat-proof bowl, whisk together the sugar, lemon juice, egg, and egg yolk.

Place the bowl over a small saucepan of simmering water and add the butter.

Cook the mixture over low heat for about 15 minutes, whisking occasionally until it reaches 180 degrees F.

Remove from heat and cover with plastic wrap. Refrigerate until fully cooled.

Whip the heavy cream to stiff peaks in a medium bowl.

Gently fold the cooled curd into the whipped cream until fully combined.

Transfer the whipped lemon curd to a piping bag and pipe onto the inside of each macaron shell, then sandwich with another shell.