Preheat oven to 180ºC . Combine the melted butter with the ginger and sugar and spread evenly on the bottom of a 10 x 36 cm baking pan. Cover with tomato slices. Meanwhile, in a mixer, cream the butter with the brown sugar and molasses. In another bowl, sift together the flour, baking powder and spices. Add flour mixture, alternately with the buttermilk to the creamed butter and sugar. Pour batter over tomatoes in baking pan. Bake for approximately 40 minutes, or until a toothpick comes out clean when testing the center of the cake. Remove from the oven, loosen outer edges with a knife and invert onto a platter larger than the baking pan. Let stand at least 5 minutes before trying to remove the pan. Serve warm with whipped cream or vanilla ice cream.