In lg. bowl cream together Butter and 1/2 cup Powdered Sugar til fluffy. Add 2 cups Flour til well blended. Spread evenly into bottom of well greased 9" x 13" baking pan. Bake @ 350 degrees for 20 minutes.
Meanwhile in a small mixing bowl, beat eggs til light. Gradually add granulated Sugar, beating til thick & blended. Add grated Lemon Peel & Lemon Juice; remaining 1/3 cup Flour & the Baking Powder til well blended.
Pour Lemon mixture over Baked Crust. Return to oven. Bake 15 to 20 minutes or til pale gold color.
Remove from oven and sprinkle evenly with powdered sugar. Let cool.