1) Preheat the oven to 350°F. Lightly grease a 9" x 13" pan.
2) To make the topping: Mix all of the topping ingredients just till medium crumbs form. Set aside.
3) To make the cake: In a medium-sized mixing bowl, beat together the butter, sugar, and flavorings until blended.
4) Add the eggs one at a time, beating just until blended after each. Scrape the bottom and sides of the bowl between additions.
5) Add the buttermilk (or milk/yogurt) alternately with the flour, mixing gently to combine and scraping the bowl after each addition. Spread the batter in the prepared pan.
6) Quickly and gently sprinkle the crumbs on top, beginning with the edges then filling in the middle.
7) Bake for 35 to 40 minutes, until a cake tester or toothpick inserted into the center comes out clean. Remove the cake from the oven, and cool it on a rack.
8) When the cake is completely cool, dust it with confectioners' sugar.
Yield: One 9" x 13" cake.