This lemon poppy seed sheet cake is a crowd-pleasing dessert that is perfect for potlucks and parties. The cake is moist, tender, and bursting with lemon flavor. The poppy seeds add a nice crunch and texture to the cake. To make this cake, you will need all-purpose flour, baking powder, salt, unsalted butter, granulated sugar, eggs, lemon zest, lemon juice, poppy seeds, and milk. The cake is baked in a sheet pan and can be served with a simple glaze or dusted with powdered sugar.