Preheat oven to 375°F. Grease a 9-inch round cake pan with butter and cover the bottom with parchment paper (if you have it). In a medium saucepan over medium heat, combine the brown sugar, 4 tablespoons (1/4 cup) of the melted butter, molasses(or honey) and 1/4 cup water and bring to a boil. Stir well and pour into prepared cake pan. Set pan aside.
Sift the flour, sugar, baking powder and salt together into a bowl or onto a sheet of waxed paper and set aside. In the bowl of an electric mixer fitted with the whisk attachment (or handmixer with standard beaters) beat the eggs and sour cream together at medium speed until well blended. Scrape down the bowl and add remaining melted butter (1/2 cup) and beat until combined. Add flour mixture and beat until smooth.
Add the cranberries to the prepared baking pan and gently press the fruit into an even layer. Dollop the batter on top and use an offset spatula to gently nudge it into place without disturbing the cranberries underneath. Bake on the center rack (with a tray underneath to catch drips. just in case)30-45min, check yours on the early side until golden-use a cake tester make sure it comes out clean. Remove from the oven and let cool in pan for 15 minutes. Run a thin knife around the inside of the pan then insert over a flat platter that is larger than your cake pan, to catch any puddling or jumping cranberries. Remove the parchment paper.
Serve warm, with freshly whipped cream. However, this cake wasn't half bad two to three days layer, kept covered at room temperature.