Preheat oven to 375 degrees and prepare muffin tin with paper liners.
In a large mixing bowl, whisk together the flour, sugar, baking powder, cinnamon, baking soda and salt.
In a medium mixing bowl, whisk together the sour cream, melted butter, eggs and vanilla until smooth.
Lightly stir the sour cream mixture into the dry ingredients, just until blended. Do not overmix.
Gently fold in the rhubarb, the batter will be thick.
Divide the batter in the muffin cups. The batter should mound a bit higher than the top of the cups.