Combine and beat together brown sugar, oil, vanilla, egg, and buttermilk.

Sift together flour, salt, baking soda, and baking powder.

Mix with liquid mixture; add rhubarb and pecans.

Place in greased muffin tins and top with mixture of cinnamon, sugar, and butter.

Bake 20 minutes at 400º or until they are brown and spring back when lightly touched.

Let cool slightly and remove from muffin pans.

I run my rhubarb through my food processor to dice.