Instructions: A big easy cake to make for a crowd. Freezes well. The name of this cake is derived from the buttery brown sugar topping that sinks into the cake as it bakes and forms a crusty layer reminiscent of a lunar landscape!

Batter: Cream together butter and sugar until smooth and creamy. Add egg and vanilla. Sift together dry ingredients and add to butter and sugar mixture 1/3 at a time, along with buttermilk. Toss rhubarb with 1 Tbsp flour and fold into batter. Spoon batter into a greased 9 x 13 inch cake pan and smooth the surface. Topping: Blend together topping ingredients and sprinkle evenly over batter.

Bake at 350F for 45 minutes or until cake has risen, browned and comes away from the edges, and skewer (or toothpick) inserted in the centre comes out clean.

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