Place the butter in a 9-inch round non-reactive baking dish. Set pan in oven long enough to barely melt butter or melt in microwave. Remove from oven, swirl pan to coat evenly with butter, set in a warm place.
Toss cranberries with sugar and walnuts, set aside.
In a mixing bowl, stir together flour, sugar, baking powder and salt. Add milk and stir until just combined. Pour the batter into the pan, it will be pancake batter thin, this is what you want. Pour cranberry mixture over batter, distributing evenly. Bake for 40 to 50 minutes or until cranberries are bubbly and soft and slightly golden. Serve warm