• Preheat oven to 350°F.

Crust

• Combine all crust ingredients in large bowl. Beat at medium speed, scraping bowl often, until mixture resembles fine crumbs. I used the wire whisk attachment for my Kitchenaid.
• Press mixture onto bottom of ungreased 13- × 9-inch baking pan. Bake for 18 to 22 minutes or until edges are very lightly browned.

Filling

• Meanwhile, make the filling. In the bowl of the mixer add the sugar, lemon juice, eggs, lemon zest, and salt. Beat at medium speed until well mixed.
• Reduce speed to low; add 1/4 cup flour and baking powder. Beat until well mixed.
• Pour filling over hot, partially baked crust. Return to oven and continue baking for 23 to 25 minutes or until top is golden brown. Cool completely.

Glaze or Powdered Sugar Topping

• If using glaze: Combine powdered sugar, 1 tablespoon butter and vanilla in small bowl. Beat at low speed, gradually adding enough lemon juice and scraping bowl often, until desired glazing consistency. Drizzle over cooled bars. Cut into bars.
• If using powdered sugar: Dust top of cooled bars with desired amount of powdered sugar.