Combine first 6 ingredients in a large bowl; cover fruit mixture and chill 8 hours or up to 1 week.
Process fruit mixture, in batches, in a food processor until smooth, stopping to scrape down sides; set aside.
Whisk together eggs, cinnamon, and nutmeg until foamy.
Beat butter and dark brown sugar at medium speed with an electric mixer until creamy. Add egg mixture, beating until blended. Add fruit puree; blend well.
Combine flour and baking powder; stir into fruit mixture. Stir in burnt sugar syrup. Spoon batter evenly into 1 greased and floured 10-inch springform pan.
Bake at 300° for 1 hour and 40 minutes or until a wooden pick inserted in center comes out clean. Cool in pan on a wire rack 1 hour; remove from pan, and cool completely on wire rack.
Pour 1 cup port wine evenly over top of cake, and let stand 10 minutes. Pour remaining 1 cup wine over cake. Wrap cake with cheesecloth; place in a covered container. Let stand 2 to 3 days. (Do not refrigerate.) Serve with whipped cream, if desired.
Note: Burnt sugar syrup is available by mail order from Eve Sales Corporation. Contact them at 945 Close Avenue, Bronx, NY 10473; or call (718) 589-6800. The syrup costs $1.75 plus shipping.