Line a jellyroll pan with parchment paper and set aside. Preheat an oven to 350 degrees F.
Whisk together eggs and sugar and place in the top of a double boiler set over mediumhigh heat. Beat until mixture is hot (about 140 degrees F). Remove from the heat and continue beating until mixture holds a limp peak. Sift together flour and salt and fold into egg mixture. Fold in butter a tablespoon at a time. Gently stir in vanilla.
Pour batter into prepared pan, spreading out as necessary to create an even surface. Bake for 13-15 minutes.
Meanwhile, prepare a rectangle of waxed or parchment paper that is the same size as the pan, and cover the paper with powdered sugar.
Remove pan from oven and immediately invert cake onto prepared paper. Remove parchment paper and trim cake to smooth sides. Let cake cool completely, then spread with Manjar Blanco. Roll cake and sprinkle the outside with powdered sugar.
To serve, slice cake to form spirals. Serve with raspberry sauce if desired.
c.1996, M.S. Milliken & S. Feniger, all rights reserved