Step 1

Place a rack in middle of oven; preheat to 325°. Pulse 1½ cups (188 g) all-purpose flour, ⅓ cup (37 g) powdered sugar, 2 Tbsp. poppy seeds, and ½ tsp. Diamond Crystal or ¼ tsp. Morton kosher salt in a food processor until combined. Add ½ cup (1 stick) chilled unsalted butter, cut into pieces, and pulse until incorporated and mixture is crumbly. Add 1 large egg yolk and pulse until just combined (dough will be very dry and powdery).

Step 2

Turn dough out into pan and press across bottom and up sides with your hands. Chill in freezer until firm, about 30 minutes. Wipe out and reserve food processor.

Step 3

Bake crust until barely golden, 25–30 minutes. Transfer pan to a wire rack and let crust cool slightly. Reduce oven temperature to 300° for baking the filling.

Step 4

While the crust is cooling, work zest of 1 large lemon into 1¼ cups (250 g) granulated sugar in a small bowl with your fingers until mixture is fragrant and sugar begins to clump together. Transfer to a food processor; add 2 large eggs, 1 large egg yolk, ½ cup (1 stick) unsalted butter, melted, slightly cooled, ⅓ cup fresh lemon juice, and ½ tsp. Diamond Crystal or ¼ tsp. Morton kosher salt and process until smooth. Add 2 Tbsp. all-purpose flour; pulse just to combine.

Step 5

Slide out oven rack and place pan with crust directly onto rack; scrape filling into crust (this will save you from transferring a very full crust to the oven). Bake tart until filling is just set (center should only jiggle slightly when gently shaken) and crust is golden around the edges, 45–50 minutes. Transfer tart to a wire rack; let cool.

Step 6

Dust tart with powdered sugar just before serving.Do ahead: Tart (without powdered sugar) can be baked 1 day ahead. Cover and chill. Bring to room temperature before serving.