Preheat oven to 350F, Line 2 large baking sheets with parchment paper, spray with pan spray.  Set aside.

In a large bowl, combine the flour, poppy seeds, baking powder, baking soda, and salt. Set aside.

In a separate bowl, whisk together sugar, eggs, lemon juice, zest, and vanilla until well combined and smooth.  Pour into the bowl with the dry mixture, stir to combine.

Divide dough in half, form into 2 long, wide loaves on the prepared pan.

Bake for 20-25 minutes, until golden brown on the outside.  Remove from oven, turn heat down to 250F.

Allow loaves to cool for 5 minutes.

Cutting on a slight diagonal, slice each loaf into ½" slices.

Arrange slices on the pans - still lined with parchment.  Bake for 15 minutes, flip each piece over and bake for another 15 minutes, or until desired texture.

Remove from oven, allow to fully cool.

Whisk together glaze ingredients until smooth. If too thick to drizzle, microwave for 10 seconds at a time, stirring until runny.

Drizzle over cooled biscotti. Allow glaze to fully harden before transferring biscotti to an airtight container.