Step 1

Heat oven to 350°F. Lightly grease 15x10x1-inch baking pan; set aside.

Step 2

Combine all shortbread ingredients except flour in bowl. Beat at medium speed, scraping bowl often, until creamy. Add flour; beat at low speed until mixture resembles coarse crumbs.

Step 3

Press dough evenly into prepared pan. Bake 30-35 minutes or until light golden brown. Cool completely.

Step 4

Combine all glaze ingredients in bowl; beat with whisk until smooth.

Step 5

Spread thin layer of glaze over cooled shortbread; sprinkle with 1 tablespoon lemon zest, if desired. Let stand 30 minutes to set.

Step 6

Cut into 2 1/2x1-inch strips.