Split vanilla bean lengthwise; scrape out seeds. Stir seeds and lemon rind into butter.

Beat egg whites at high speed with an electric mixer until foamy. Add sugar, 1 tablespoon at a time, beating until stiff peaks form and sugar dissolves (5 to 6 minutes). Fold butter mixture into the meringue.

Whisk together flour and next 4 ingredients. Gently fold dry ingredients into meringue. Carefully spoon batter into a lightly greased 15- x 10-inch jellyroll pan; spread to edges of pan.

Bake at 350° for 14 minutes or until golden. Cool cake completely. Cut cake into squares. Top each piece with a dollop each of orange marmalade and crème fraîche.