Grease a 9-inch springform pan and line bottom with a parchment paper circle. Wrap outside of pan with aluminum foil to seal out water.
Preheat oven to 325° F.
Strain seeds from preserves by pressing through a wire-mesh sieve. Place preserves, chocolate and butter in a double broiler. Heat over medium heat, stirring until melted. Remove from heat.
In a large bowl, mix sugar, eggs and flour. Add chocolate mixture. Mix gently.
Pour into springform pan. Place springform pan in a larger baking pan. Add about 1 inch of water to outside pan, forming a water bath. Bake at 325° F until top is dry and skewer comes out clean, about 45 minutes. If water evaporates, replenish .
Let cool, unmold and turn upside down. Remove parchment paper. Place on serving plate and dust with powdered sugar.
Serve individual slices with Raspberry Sauce.