Preheat Oven to 375. Cream together butter and sugar. Separately, whisk milk, egg and vanilla. Add to creamed mixture and blend well.
Sift together dry ingredients and mix gently with the above. Place in a buttered cake pan - round is pretty when cut.
Make the crumble topping with the cold butter, 1/2 cup flour & sugar and salt pulsing in the food processor or crumble with 2 forks. Cover the batter with the crumble topping and bake for 35 minutes until golden brown. Allow to cool a few minutes before serving.
Dredge with a little confectioner's sugar and serve with fresh unsalted room temperature butter!