Heat oven to 350*.Coat a 13x9" baking pan with nonstick cooking spray -- set aside.
to prepare the cake: combine cake mix, sour crea,m, eggs, vegetable oil and lemon zest in a large bowl -- beat on low speed for 30 seonds then on medium high for 2 minutes. Fold in 1 1/2 cups of cranberries -- pour batter into prepared baking pan --
bake at 350* for 30 minutes.
meanwhile, make topping: in a medium sized bowl, whisk together the flour, browm sugar, cinnamon and nutmeg and salt. stir in butter until mixture is moistened and starts to clump together.carefully remove the cake from the oven -- sprinkle crumb evenly over the top -- scatter with remaining cranberries and then return to the oven and bake at 350* for an additional 20 minutes -- remove pan to wire rack and cool completely --
dust lightly with confectioners' suar and cut into 16 squares.