Cream the butter and sugar together until smooth.
Add the eggs, lemon juice, and vanilla. Continue mixing on medium-high speed until the added wet ingredients are fully incorporated.
Whisk in the flour, baking powder, baking soda, and poppy seeds until no dry clumps remain and the poppy seeds are evenly distributed.
Divide the batter among the tin evenly.
Bake at 350 degrees F for 20 minutes. Enjoy!