Grind almonds in electric blender or pound in mortar to fine paste. Beat three whole eggs and three yolks with sugar and salt until thick and light yellow.
Fold in three egg whites beaten to stiff peak. Gradually sift in flour mixed with ground almonds.
Fold no more than necessary to make an evenly blended mixture. Pour into 9-inch loaf pan either lined with wax paper or lightly buttered and sprinkled with flour.
Bake 25 to 30 minutes in 375F oven or until toothpick inserted in middle of cake comes out clean.
Invert cake over rack or wax paper sprinkled with powdered sugar.
If you have used wax paper, cake will come out instantly; wait until it cools to remove the paper on which it baked. If you have not used wax paper, leave cake inverted in pan until cool. Sprinkle with powdered sugar just before serving.