Preheat oven to 350 degrees and set a rack in the middle level. Line a jelly-roll pan or cookie sheet with parchment or foil.

In a mixing bowl, whisk eggs and salt until liquid. Whisk in sugar and vanilla smoothly. Whisk in butter or oil, then stir in nuts. Combine flour with baking powder and cinnamon and stir with a dry whisk to mix. Fold flour mixture into egg mixture until all the flour is absorbed - the dough will be very soft. Use a spoon to form two logs of dough on the prepared pan, adjusting the sides with the tip of the spoon to make the logs even. Bake the logs of dough about 30 minutes, or until well risen and firm when pressed with a fingertip. Cool on pan to room temperature.

Slice baked logs diagonally about 1/4 to 1/2-inch thick, using a sharp serrated knife. Return biscotti to pan, cut side down, and bake up to 20 minutes longer, or until biscotti are a deep golden color. Cool on pan and store in a tin.