In a small bowl, use your fingertips to rub the lemon zest into the sugar until fragrant.

In the bowl of a stand mixer fitted with a paddle attachment, beat the butter and lemon-sugar mixture on medium speed until pale and fluffy (about 5 minutes).

Scrape down the sides of the bowl, then add the lemon juice, egg, egg yolk, and vanilla extract. Beat again until light and fluffy.

In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add to the wet ingredients, mixing on low until just combined. Fold in the poppy seeds until evenly distributed.

Cover and refrigerate for at least 1 hour (or up to overnight).

When ready to bake, preheat the oven to 350°F (175°C). Line several baking sheets with parchment paper.

Using a cookie scoop, portion the dough into 2–3 tablespoon balls. Space them about 2 inches (5 cm) apart on the baking sheets.

Optional: In a small bowl, make the lemon sugar coating. Rub the lemon zest into the sugar, then roll each dough ball in the mixture and return to baking sheet.

Bake for 12–14 minutes, or until the edges are lightly golden brown.

Let the cookies cool on the tray for 5 minutes before transferring to a wire rack.