1. Prepare the Crust:

1. Preheat oven to 350°F (175°C). Pour melted butter into a 9-inch round cake pan and sprinkle brown sugar evenly over the butter.
2. Arrange pineapple rings over the brown sugar mixture, then fill the centers and gaps with fresh cranberries.
3. In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
4. In a large bowl, beat softened butter and granulated sugar until light and fluffy. Add eggs one at a time, then stir in vanilla.
5. Alternately add the flour mixture and milk to the butter mixture, beginning and ending with the flour mixture. Mix until just combined.
6. Spread batter evenly over the pineapple and cranberry layer in the cake pan.
7. Bake for 40-45 minutes or until a toothpick inserted in the center comes out clean.
8. Let cool in pan for 10 minutes, then invert onto a serving plate. Serve warm or at room temperature.