I have not tried this and I don't recommend substituting the egg for a flax egg. My friend, Megan, has a wonderful looking u003ca href=u0022https://shortgirltallorder.com/vegan-lemon-poppyseed-muffinsu0022 target=u0022_blanku0022 rel=u0022noreferrer noopeneru0022u003evegan lemon poppy seed muffinu003c/au003e on her site though! Be sure to check that out if you're looking for a vegan version.