using paddle attachment, beat almond paste on low speed until it breaks up
slowly add granulated sugar in stream, beating until incorporated (if added too quickly, paste won't break up as well)
on low speed, add butter 1T at a time for ~1minute, scrape down sides of bowl
on medium speed, and beat until light and fluffy, 3-4 minutes
still on medium, add egg mixture in very slow, steady stream and mix until incorporated, scrape down sides of bowl
mix ~30 seconds on medium
add poppy seeds and citrus zest and mix by hand
add flour mixture in two batches, mixing until incorporated
put in prepared pan