Preheat oven to 375 F and let the oven heat for 15 minutes before baking. To a muffin/cupcake pan, add liners.
In a small bowl, add soy milk and apple cider vinegar. Stir to combine and let sit for 5 minutes (it will curdle as it sits).
In a large bowl, add oat flour, whole wheat flour, baking powder and baking soda. Stir well to combine thoroughly.
In a medium bowl, add sugar and butter and stir to combine. Add lemon zest, lemon juice, vanilla, and poppy seeds. Stir to combine.
Add the soy milk mixture into the sugar mixture and stir to blend. Then add the wet mixture to the dry flour mixture. Stir with a large spoon to combine. Do not over-mix; some clumps will remain.
Quickly pour batter into each muffin liner, each 3/4 full. Bake at 375 F for **20-25 minutes or until toothpick inserted in the middle comes out clean. Let cool.
To make the lemon glaze- in a small bowl, add the powdered sugar and lemon juice. Stir well with a spoon until blended. Drizzle 1-2 teaspoons over each cooled muffin. Let sit 5 minutes before serving (icing will harden). Makes 12 muffins. Store in airtight container in the fridge for up to a week.