In a large bowl, cream together 1/2 cup of the butter and confectioners sugar. In a separate bowl, stir together the flour and salt. Gradually add the flour mixture to the creamed mixture.
With floured hands, pat dough evenly into an ungreased 9-inch square baking dish. Bake at 350°F for 12 to 15 minutes or until lightly colored.
Meanwhile, in a small saucepan, melt the remaining 1/4 cup butter. Stir in the brown sugar, water and lemon juice; bring to a boil, stirring constantly. Remove from heat, and stir in almonds and almond extract.
Spread almond mixture evenly over shortbread base. Return to oven, and bake an additional 12 to 15 minutes until golden brown. Cut into bars while still warm but not hot.