Preheat oven to 350°.

In a large bowl, blend the shortening and brown sugar together. Add the buttermilk, egg and vanilla and blend together. Add the dry ingredients to the bowl and mix just until well combined. Fold in the rhubarb and spread in a greased 9x13 pan.

In a small bowl, mix the sugar and cinnamon together. Add in the pecans and coconut if you are using them. Spread the mixture over the top of the batter.

Bake at 350° for 40-50 minutes, or until a toothpick comes out clean in the center. Allow to cool at least 20 minutes before serving.

OPTIONAL: Top with additional toasted coconut and pecans. Serve with whipped cream or ice cream.