Heat oven to 425 and spray a donut pan with cooking oil.Combine the sifted flour with the other dry ingredients and set aside.Beat the eggs, lemon juice and zest, and sour cream. Add poppy seeds and stir.Add the wet to the dry and mix to combine. Don't over mix the batter.Fill a pastry bag or ziplock with the batter and cut the tip about two inches up. If the opening doesn't give you a wide enough strip of batter, just cut off a little extra.Fill the cavities about ¾ full and smooth over any edges with a spoon (or finger) dipped in a little oil or melted butter.Bake the donuts for exactly 7-9 minutes or just until the tops brown.Cool in the pan for 5 minutes, then sugar them or add icing.Whip the butter, extract and sweetener together. To thin, add 1 tsp warm water and a time until desired consistency. This icing won't taste amazing warm BUT will taste like sweet lemon butter when cooled, which is amazing.