Ultimate Sour Lemon Bars

Crust:
1 1/2 Cups all-purpose flour
1/4 Cup Powdered Sugar
1 Pinch salt
1/2 Cup unsalted butter -- Cut In Pieces
1/2 Teaspoon vanilla extract

Topping:
5 Large eggs -- room temp
2 Cups sugar
1 Cup lemon juice, fresh -- strained
3 Tablespoons all-purpose flour
2 1/2 Tablespoons lemon peel -- grated

Preheat oven to 350ºF. Line 9" square pan with foil, extending 1" above sides of pan. Grease uncovered 2 sides of pan. Combine flour, powdered sugar and salt in processor. Add butter and cut in using on/off turns until mixture appears sandy. Add vanilla and process until dough begins to come together. Press evenly into prepared pan. Bake until golden brown, about 28 minutes.

Meanwhile, prepare topping: Whisk eggs and 2 Cups sugar in medium bowl to blend. Whisk in lemon juice, then flour. Strain into another bowl. Mix in grated lemon peel. Reduce oven to 325ºF. Pour filling over hot crust. Bake until sides are set and filling no longer moves in center when pan is shaken, about 22 minutes Cool on rack . Cover and chill at least 4 hours. Using foil sides as aid, lift dessert from pan. Fold down foil sides. Cut into 16 squares. Cut each square diagonally in half, forming triangles. Sift top with additional powdered sugar.