Preheat oven to 375 degrees F and spray non-stick 12 muffin tin with cooking spray. Set aside.
Add egg, milk, yogurt, oil, maple syrup, vanilla extract, baking powder, baking soda and salt. Whisk well until combined and no small lumps are visible. Add flour and mix gently with spatula just enough to combine. Do not overmix and a few white flour patches are fine.
In a small bowl, combine 1 1/2 cups rhubarb and 1 tablespoon of flour, and stir. Add to a muffin batter and fold a few times until incorporated.
Distribute batter evenly between 12 openings of a muffin tin (I used regular ice cream scoop) and top with remaining rhubarb. Bake for 20-22 minutes or until a toothpick inserted in the center comes out clean.
Remove rhubarb muffins from the oven and let cool for 10 minutes. Enjoy!
Notes
Frozen rhubarb: Be sure to thaw and lightly squeeze.
Store: On a plate on a kitchen counter covered with a towel for 1 day. Then transfer muffins to a container with a lid and into the fridge for another 3 days.
Freeze: Bake, cool and place muffins in an airtight container or loosely covered container. Freeze for up to 3 months. To thaw, just place one muffin on a counter for a few hours or microwave.