Preheat oven 350. Lightly butter and flour 13x9 baking pan.
Prepare fruit sauce: Combine the applesauce, cranberries, sugar and cinnamon in a saucepan; bring to a simmer over med-hi heat. Simmer, stirring frequently, just until the cranberries begin to pop open, about 5 minutes. Remove from heat and set aside to cool.
Prepare topping: In a mixing bowl, stir the flour with the brown sugar. Using your fingertips or the tines of a fork, quickly work in the butter to form coarse crumbs. Set aside.
Prepare cake batter: In a large mixing bowl, cream the butter and sugar together with mixer on high until light and fluffy. Add the eggs one at a time, beating well after each addition and scraping down the sides of the bowl as needed. Stir in the vanilla.
In another bowl, whisk together the flour, baking powder and salt. Add this to the creamed mixture in batches, alternating with the milk and blend until smooth.
Spread the batter in prepared pan, and spread the cooled cranberry applesauce evenly on top. Sprinkle with the topping; bake until it is bubbling hot and crisp, 40-45 minutes. Remove the cake from the oven and cool completely in the pan. Shortly before serving, cut into squares.