Preheat the oven to 350 degrees F.
Butter the bottom and sides of a 9-inch cake pan with 3 tablespoons butter, sprinkle 1/2 cup of the sugar evenly over the bottom, and arrange the cranberries in the pan.
In a bowl with the mixer cream together the remaining 6 tablespoons butter and 1/2 cup sugar. Add the egg, vanilla, and orange rind and beat the mixture until well combined.
Into another bowl sift together the flour, baking powder, and salt. Stir the dry ingredients into the butter mixture, 1/2 cup at a time, alternately with the milk until it is combined. Pour the batter over the cranberries and smooth the top. Bake the cake on a baking sheet in the middle of the oven for 30 to 45 minutes, or until an inserted toothpick comes out clean.
Transfer the cake to a rack and let it cool in the pan for 20 minutes. Run a thin knife around the inside of the pan and invert the cake stand.
In a small saucepan melt the currant jelly over low heat, stirring, and brush it over the cake. Serve the cake warm or at room temperature with the whipped cream, if desired.