Preheat Oven To 350 Degrees. Cut Squash In Half If Whole And Discard Seeds. Place Calabaza Flesh Side Down On Cookie Sheet And Bake For 30 Minutes. Melt Butter Over Medium Heat In Soup Pot. Add Onions, Coriander, Cumin, Salt And Pepper. Cover And Cook Until The Onions Are Soft About 20 Minutes. Add Chicken Stock And Bring To A Boil. Add Plaintain, Cover, Simmer For 10 Minutes. Remove Calabaza From Oven And Allow To Cool. Scoop Out Calabaza Flesh And Break Into Small Pieces, Add It To The Soup. Add Apple Juice And Simmer For 30 Minutes. You Can Either Serve It At This Point Or Put It Through A Strainer And Reserve Liquid. Take The Solids And Puree. Return Puree To The Liquid And Bring Back To A Simmer And Serve.