Line bottom of greased 10 inch tube pan with circle of parchment or brown paper. Grease paper.

In large bowl, cream butter. Beat in sugar until smooth and fluffy. Beat in egg yolks. Sift flour with salt, then stir about 1/3 of flour mixture into butter mixture. Combine 1/2 cup Kahlua with coffee. Stir 1/3 cup of Kahlua/coffee mixture into batter. Continue to alternate flour and liquid until used. Stir in nuts. In large bowl, beat egg whites until foamy. Beat in cream of tartar, then beat until stiff, but not dry. Carefully fold egg whites into batter. Transfer to prepared pan. Bake at 275 for 2 to 2 1/2 hours or until top is golden and sides of cake are pulling away from pan. Set on wire cooling rack and drizzle remaining 1/2 cup kahlua over top. Cool 30 minutes, then remove from pan and cool completely. Before serving, sift mixture of powdered sugar and expresso/coffee powder on top.