Here's my favorite al time Lemon Poppy seed Muffin recipe (from Eric Nagy):

Mix wet ingredients completely but gently with whisk. (It is best not to add the butter until ready to mix wet and dry together, otherwise it may get lumpy as it sits.) Combine dry ingredients. When grating the lemons, remove only the yellow outer layer, as the white is very bitter. Stir together wet and dry until just mixed-do not over mix. Fill buttered or paper lined muffin tins generously. Cook immediately. Batter does not store well.

Cooked muffins also do not last long unless frozen, in which case they do quite well. (Cooked muffins also do not last long because they're very yummy.)

I cook them for 20 minutes at 325 - 350 F. in a convection oven or for the same length of time at 400 F. in a conventional oven. Makes 2 dozen.