To make cinnamon-swirl, combine meltedbutter, brown sugar, walnuts, flour and cinnamon until blended. Set aside.
In a large bowl stir together flour, sugar, baking powder, salt and dry milk.
Add oil, eggs and water. Stir until combined. The batter will be lumpy.
Spoon half the batter into a greased 8-inch square pan. Sprinkle with half the swirl. Spoon remaining batter over and top with remaining swirl.
Bake 30-35 minutes or until top is well-browned. Serve warm or at room temperature.