Ingredients: lemon, rhubarb, flour, oat flour, brown sugar, baking powder, salt, egg, oil, milk, vanilla, and powdered sugar.
Set oven to 400 degrees. Line a muffin tray with paper liners or spray with oil and coat tray with a light dusting of flour. In a medium bowl, mix 1 1/2 cups flour with 1/2 cup oat flour, 2 1/2 tsp baking powder, 1/3 cup brown sugar, and 1/2 tsp salt. In another bowl, mix 1 egg, 1/4 cup oil, 1 cup milk, 2 Tbsp lemon zest, 3 tsp lemon juice, and 1 tsp vanilla. Create a crater in the dry ingredients and pour the wet ingredients into the dry ingredients. With a spatula gently fold in mixture until the batter is well combined and lumpy (do not over mix). Fold in 2 cups of diced fresh rhubarb. Place in oven for 20-25 minutes. For a lemon glaze, mix 1/3 cup powdered sugar with 1 1/2 tsp milk and 2 tsp lemon juice. A few minutes before the muffins are done, pull out of the oven and drizzle with the lemon glaze. Return to the oven until the muffins are a golden brown. Remove from the oven when a toothpick inserted in a muffin comes out clean. Top muffins with any remaining glaze. Let cool or eat warm.