Preheat the oven to 350 degrees F. Generously spray 8 cavities of a muffin tin with nonstick spray. Do not use muffin liners as these muffins will stick to the paper.
Zest a large lemon and then juice the lemon. Combine the 1/2 tablespoon lemon zest and 2 and 1/2 tablespoons lemon juice in a bowl with the honey, sugar, yogurt, and vanilla extract. Stir together and then add in an egg. Stir until combined.
In a blender or food processor, blend regular old fashioned or quick oats until they reach a flour consistency. Measure the oat flour AFTER blending and not before.
In another bowl, stir together the chia seeds, oat flour, and baking soda.
Combine the wet and dry ingredients and mix until just combined. Over stirring the muffins will result in dense muffins.
Add more lemon zest if desired and then pour the muffin mixture into the prepared muffin tin. You can fill them pretty full as these muffins don't rise too much.
Bake for 18-20 minutes or until lightly golden on top and a toothpick comes out clean when inserted in the center. Remove from the muffin tin and allow to cool.
If desired, mix a glaze by stirring together the powdered sugar, vanilla, and lemon juice. Start with 1/2 teaspoon of lemon juice and add more if needed to thin. It does not require a lot of liquid to make the thick glaze. Pour the glaze evenly over the muffins when they are no longer hot and allow to set-up on the muffins.
Store in an airtight container and eat within 3 days.
Notes
The glaze is delicious, but makes these less healthy. If you want a healthy muffin omit the glaze.