My aunt used to make this "special holiday" cake during the Christmas season. She would put the cake on a Christmas-themed plate and place mint sprigs around the cake on the plate for a pretty presentation. This is a very sweet-tart tasting cake that has a refreshing after taste.
Lightly spray a 9"-spring form pan w/ cooking spray. In medium saucepan over low heat, Stir 4 tbsp butter and 3/4 cup brown sugar until melted. Remove pan from heat and stir in cranberries.
Pour cranberry mix into bottom of pan. Smooth it out with a spatula. Heat oven to 350. In small bowl, whisk together eggs and vanilla. In lg bowl, combine flour, baking powder, baking soda and salt.
In another lg bowl, cream remaining butter for 2 mins, until fluffy. Add sugar and mix well. Beat in egg mix and then sour cream. Lastly, gently mix in flour mix until just combined. Pour mix over cranberry mix. Bake 50-60 mins. Let cool at least 15 mins. Put a lg plate over top of pan and gently flip over until cake is on plate w/ cranberry sauce on top.