Beat butter and 2 cups sugar at medium speed with an electric mixer 5 to 7 minutes. Add egg yolks, 1 at a time, beating just until yellow disappears.
Stir together 1/2 cup bourbon and vanilla. Add flour to butter mixture alternately with bourbon mixture, beginning and ending with flour. Beat at low speed just until blended after each addition.
Beat egg whites at high speed with an electric mixer until foamy. Add remaining 1 cup sugar, 1 tablespoon at a time, beating until stiff peaks form and sugar dissolves (2 to 4 minutes). Fold into cake batter.
Sprinkle half of pecans into bottom of a greased and floured 10-inch tube pan. Fold remaining pecans into cake batter, and pour into pan.
Bake at 350° for 1 hour and 25 minutes or until a long wooden pick inserted in center comes out clean. Cool cake in pan on a wire rack 10 to 15 minutes; remove cake from pan, and cool on wire rack.
Moisten several layers of cheesecloth with remaining 1/2 cup bourbon; cover cake completely with cheesecloth. Place in an airtight container, and store in a cool place 1 week, remoistening cheesecloth as needed. Sprinkle with powdered sugar just before serving.