2/3 c. firmly packed brown sugar
2/3 c. chopped walnuts
1 tsp. cinnamon
3/4 c. butter, softened
3/4 c. sugar
2 eggs
3/4 c. sour cream
3/4 tsp. vanilla
1 1/2 c. flour
1/2 tsp. baking soda
1/2 tsp. baking powder
1/4 tsp. salt

Combine brown sugar, walnuts and cinnamon. Stir until cinnamon is well blended. Set aside.

Cream butter and sugar with an electric mixer until light and fluffy. Add eggs and beat well. Beat in sour cream and vanilla. Thoroughly blend into egg-sour cream mixture.

Spoon half of the batter into a buttered 8 or 9 inch square baking dish. Sprinkle 1/3 of the brown sugar mixture evenly over the top. Evenly spoon remaining batter over the brown sugar mixture. Sprinkle with remaining brown sugar mixture.

Shield each corner of the dish with a 2 inch triangle of foil to keep corners from over-baking. Microwave on MEDIUM HIGH (70%) for 9 minutes, turning dish a quarter turn every 3 minutes. Remove foil triangles after 6 minutes. Increase power to HIGH and microwave 3-5 minutes longer or until cake tests done. Cool on cutting board for at least 15 minutes before cutting.