Rhubard Cake

I made this recipe last night and for some reason thought it was for cupcakes....well, they TASTE great, they just kind of crumbled out of the muffin cups. So next time I'll make this in a cake pan. They are super moist & VERY yummy! Just thought I'd share for anyone interested.
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Rhubarb cake
INGREDIENTS
1/2 cup white sugar
1/2 cup chopped walnuts
1 tablespoon butter
1 teaspoon ground cinnamon
1 1/2 cups packed brown sugar
1/2 cup shortening
1 egg
2 cups all-purpose flour
1/2 teaspoon salt
1 teaspoon baking soda
1 cup sour cream
1 1/2 cups chopped rhubarb
DIRECTIONS
Preheat oven to 350 degrees F. Grease and flour 13 x 9 x 2 inch pan.
Mix sugar, nuts, melted butter and cinnamon until crumbly and set aside.
In a separate bowl, cream together brown sugar, shortening and egg.
Add flour, soda and salt to creamed mixture alternately with sour cream. Lastly, stir in rhubarb.
Pour mixture into pan and sprinkle with reserved topping.
Bake at 350 degrees F for 45 to 50 minutes. Cut in squares and serve warm or cool.