Preheat oven to 350° F. Prepare a baking sheet by greasing lightly or lining it with parchment paper.
Making sure you only cut through the rind of the Camembert cheese, run a knife around the top (1/4-inch in from the edge of the cheese). Make several cuts across the cheese forming small triangles, and then gently remove the top rind forming a shallow cup to hold the jam.
Spread the jam over the top of the cheese. Sprinkle the rosemary and nuts on top. Place on baking sheet and bake 20 minutes, or until the cheese is warm and soft.
Transfer cheese to a serving dish with a spatula. Serve warm with crackers or French bread toasts.