Preheat oven to 350 degrees F.
Grease a round 9" baking tray with butter and flour. Throw away the excess flour.
In a large bowl, combine the dry ingredients for the cake... flour, baking powder and salt. Set aside.
In another bowl, combine the butter and sugar. Beat for about 5 minutes using an electric mixer until the mixture is light and fluffy.
Add the eggs and vanilla. Beat for a few more minutes until light and creamy in texture.
Now add the half the dry ingredients. Add the buttermilk. And then add the remaining dry ingredients. DO NOT OVER MIX!
Here is your batter.
Add the chopped cranberries and using a spatula, fold into the batter.
Spread the cake batter into the greased 9" tray.
Now make the crumb topping by combining all the ingredients into a bowl. Stir well.
Add the crumb topping over the cranberry cake.
Into the oven for 40 minutes, you may start checking the cake at the 35 minute mark.
Serve warm or cold.