Preheat oven to 350°F (180°C).
For Crust: Beat butter and sugar together in a large bowl at medium speed of mixer until creamy. Add flour and salt; mix on low speed until blended. Spread dough evenly into bottom of a greased 8-inch (20 cm) square baking pan. Bake 15 to 20 minutes until crust is golden.
For Filling: Beat eggs and sugar in a large bowl at medium speed. Beat in butter, corn syrup, flour, buttermilk, vanilla and lemon peel if desired, until mixture is smooth. Pour filling over baked crust.
Bake 20 to 25 minutes until edges just begin to brown and filling is set. Cool completely. Sprinkle with powdered sugar and cut into bars.
Note: Recipe can be doubled and baked in a 13 x 9-inch (33 x 23 cm) baking pan. Bake time may vary by a few minutes, so watch carefully.