Line 13x9-inch baking pan with aluminum foil, then spray with nonstick cooking spray; set aside.
In large bowl, with electric mixer, beat Imperial spread and 1/2 cup granulated sugar until light and fluffy, about 3 minutes.
Beat in 2 cups flour until fine crumbs form.
press into prepared pan. Bake uncovered 20 minutes.
Meanwhile, in medium bowl, with electric mixer, beat eggs, remaining 2 cups granulated sugar, remaining 1/3 cup flour, lemon juice and lemon peel 4 minutes or until light and fluffy; pour over hot baked crust.
Bake an additional 25 minutes or until lemon minxure is just set.
On wire rack, cool completely.
Using foil, lift out of pan. spray knife with nonstick cooking spray and cut into triangles.
To serve, sprinkle generously with confectioner's sugar.