Preheat your oven to 350 degrees Fahrenheit now. Butter your round baking pan very well. This prevents the fruit from sticking later.
Melt butter and brown sugar in a saucepan. Stir it until the mixture is smooth. Pour this into the bottom of the pan.
Spread the fresh cranberries over the sugar mixture. Make sure they cover the bottom evenly. Press them down slightly into the sweet syrup.
Whisk the flour, baking powder, and salt together. Set this dry mixture aside for a moment. Ensure there are no large clumps of flour.
Cream the butter and white sugar until fluffy. Use your electric mixer on a medium speed. This takes about two or three minutes.
Add the eggs one at a time now. Beat well after you add each egg. Pour in the vanilla extract for extra flavor.
Add the flour mixture and milk in stages. Start with flour and end with flour. Mix until the batter is just combined.
Spread the batter over the cranberries very carefully. Use a spatula to smooth out the top. Do not disturb the berries underneath it.
Bake the cake for about forty-five minutes. The top should be a golden brown color. A toothpick should come out clean and dry.
Let the cake cool for fifteen minutes only. Run a knife around the edges very slowly. Invert the cake onto a large serving plate.