Cream butter; gradually add sugar, beating well. Add eggs, one at a time, beating well after each addition. Stir in vanilla.
Combine 2 cups flour, cocoa, baking powder, soda, and salt; add to creamed mixture alternately with water, beginning and ending with dry ingredients. Mix well after each addition. Dredge sauerkraut and pecans in remaining 1/2 cup flour; stir to coat well. Stir mixture into batter.
Spoon batter into an un-greased 15- x 10- x 1-inch jellyroll pan. Bake at 350° for 35 to 40 minutes or until a wooden pick inserted in center comes out clean. Cool completely. Frost with Rich Butter Frosting. Cut cake into squares to serve.