For crust: Preheat oven to 350°F. Line 8-inch square baking pan with foil; butter foil. Mix flour, sugar and salt in processor. Add butter and nuts and blend until fine meal forms. Press into bottom of prepared pan. Bake until golden brown, about 20 minutes. Meanwhile, prepare filling: Blend 3/4 cup sugar, eggs, lime juice, 1 tablespoon grated lime peel, baking powder and salt in processor until smooth. Pour filling onto hot crust. Bake until filling begins to brown and is just springy to touch, about 20 minutes. Cool completely in pan on rack. Lift foil and cookies from pan. Gently peel foil from edges. Cut into 16 squares. (Can be prepared 1 day ahead. Wrap tightly and refrigerate.) Sift powdered sugar over. Garnish each with lime peel. Serve at room temperature. cook 036