Combine first 5 ingredients in a large bowl; stir well. Combine pumpkin, eggs, and vanilla, stirring well with a wire whisk. Slowly add pumpkin mixture to flour mixture, stirring until dry ingredients are moistened. (Mixture will be very crumbly; it will gradually become moist after stirring.)
Melt butter in a large skillet over medium heat; add macadamia nuts. Cook, stirring constantly, until nuts are browned. Remove from heat, and cool completely. Knead or gently stir cooled nuts into dough.
Place dough on a lightly floured surface, and divide into 4 portions. Lightly flour hands, and shape each portion into a 1" x 15" log. Place logs 3" apart on lightly greased large cookie sheets.
Bake at 350° for 23 minutes; cool logs 15 minutes. Reduce oven temperature to 300°.
Cut each log crosswise into 1/2" slices, using a serrated knife. Place slices on ungreased cookie sheets. Bake at 300° for 15 minutes. Cool completely on wire racks.