In a large bowl, mix together cake mix, pudding mix, sour cream, oil, beaten eggs, and water.
In a small, microwaveable bowl, melt ½ cup white chocolate chips in 15-30 second intervals, stirring in between, until smooth. Pour melted chocolate into the cake mixture and stir until blended.
Fold in the remaining white chocolate chips.
Generously spray a 9" bundt pan with cooking spray. Pour in half of the batter, then top with raspberry jam. Top with the remaining batter.
Bake 45-50 minutes, or until top is springy to the touch and a wooden toothpick inserted comes out clean.
Cool cake thoroughly in pan for about 90 minutes before inverting onto a plate. If desired, pipe the top with cream cheese frosting.
Frosting
Cool cake thoroughly in pan for about 90 minutes before inverting onto a plate. If desired, pipe the top with cream cheese frosting.
Slowly beat in powdered sugar until smooth. You can add more or less powdered sugar to reach the consistency you desire.
Pipe the icing onto cooled cake.
Notes
If you're worried about your jam sinking to the bottom, you can swirl it slightly with a knife or toothpick for a more "marbled" look.