Preheat oven to 375 degrees, with the racks in the upper and lower thirds. Line 2 baking sheets with parchment paper.

In a medium size mixing bowl, combine the flour, poppy seeds, baking powder and salt. Whisk to combine. Set aside.

In a stand mixer with the paddle attachment (or large mixing bowl with a hand mixer) beat the butter and sugars at medium speed for 2 minutes, until light and fluffy. Scrape down the sides of the bowl if necessary. Add the egg, vanilla, lemon zest and lemon juice and beat for over medium speed for 1 minute, until combined. Add in the flour mixture, and beat of low speed until just combined. Scrape down the bowl if necessary.

Use a medium cookie scoop* (or manually measure 1.5 tablespoon balls), scoop out the cookies and transfer to parchment lined cookie sheets. Bake in the oven for 16 minutes, rotating the trays half way thru baking. Cool for 3 minutes before eating. Will keep in an airtight container for 1 week.

This dough freezes beautifully. Just freeze the scooped dough on a cookie sheet. Once frozen, transfer to a freezer safe container. Bake an additional 2-4 minutes than when baked raw.