-
Preheat oven to 425 degrees F. Line muffin pan with cupcakes liners.
-
In a large bowl, whisk together flour, baking powder, baking soda, salt, and sugar.
-
Create a well in the center of the flour mixture and add oil, eggs, buttermilk, and vanilla.
-
Whisk together until all ingredients are incorporated. Batter will be thick!
-
Stir in sliced rhubarb.
-
Spoon batter into muffin cups ⅔ of the way full.
-
To make the streusel, add sugar, flour, and melted butter to a small bowl. Stir together with a fork until mixture is crumbly. Sprinkle on top of the muffin batter.
-
Bake muffins for 5 minutes at 425 degrees, then reduce the oven temperature to 350 degrees and bake for an additional 15-17 minutes or until tops are slightly golden and when a toothpick is inserted in the center of the muffin and comes out with a few crumbs.