Heat oven to 350 degrees F. Grease and flour a 12 cup bundt or tube pan.
Mix flour, salt, baking powder, baking soda, cinnamon and allspice in a large bowl.
In a separate bowl mix 1/2 cup cider reduction, brown sugar, eggs, melted butter, and vanilla until blended.
Peel, core and seed apples, then shred using a food processor or box grater.
Add cider mixture to dry ingredients, mixing just until blended. Stir in shredded apples.
Pour into prepared pan, smoothing top.
Bake at 350 degrees for 55 minutes to 1 hour and 5 minutes, or until a skewer inserted in the middle comes out clean.
Transfer bundt pan to a sheet pan with a wire rack. This will help catch spills. Cool 10 minutes, then brush with 1 Tablespoon cider reduction. Invert cake then brush the top and sides of the cake with the remaining cider reduction.
Cool glazed cake an additional 20 minutes, then stir prepared cider glaze and drizzle over cake. Let cool completely before serving.