How to Make It
Preheat the oven to 400º. Line a 6-muffin tin with large paper cups, and set aside.
In a large bowl, rub the sugar and lemon zest together with your hands until the sugar and lemon juice are combined. Whisk in the flour, baking powder, baking soda, salt, and flax seed meal. In a separate bowl, whisk the sour cream, eggs, vanilla, lemon juice and melted butter together until until all of the ingredients are blended. Pour the wet ingredients over the dry ingredients and stir to blend. Stir in the poppy seeds and 2 tablespoons of the flax seeds.
Using a measuring cup or scoop, evenly divide the batter between the muffin cups. Sprinkle the remaining flax seeds on top of the muffins. Bake, uncovered, for 20 to 30 minutes or until the tops begin to turn golden brown and a toothpick inserted in the middle of a muffin comes out clean. Cool the pan on a rack for 5 to 10 minutes before serving.
Because store-bought flax seed meal lacks the nutritional value of whole flax seeds, it's best to make a fresh, coarse-ground flax seed meal just before you use it. Flax seed meal is easy to make with a with a food processor, clean coffee grinder, or blender. One cup of whole flax seeds yields about 1 2/3 cups of flax seed meal, so leave room for expansion (use any leftover flax seed meal in smoothies or sprinkled on top of cereal or yogurt).