Combine sugars and wet ingredients into a bowl; stir in dry ingredients; dump in rhubarb.

Fold in rhubarb until just combined.

Fill lined muffin tin about 2/3 of the way with batter.

Make topping: combine sugar, butter, and cinnamon in a small bowl. Top each muffin with 1 teaspoon of mixture.

Bake at 350℉ for 18-22 mins; remove muffins from tin to cool.

The perfect breakfast for rhubarb season!