1. Preheat oven to 350 degrees F.
2. In a bowl, mix 2 cups flour and 1/2 cup sugar. Using a pastry blender or fork, cut in butter until lumps are gone. Or, blend flour and sugar in a food processor; add butter and process until the consistency of cornmeal. Press mixture into the bottom of an ungreased 9-by-13-inch pan. Bake until golden around the edges and slightly firm to the touch, about 18 to 20 minutes.
3. While crust is baking, prepare filling. With an electric mixer, beat eggs on medium speed. Gradually add 1 1/2 cups sugar while continuing to beat. Mixture should be thick and lemon colored. Mix in salt and 3 tablespoons flour. Stir in lemon juice and lime zest and mix until smooth, about 20 to 30 seconds.
4. When crust is done baking, pour filling into pan, spreading it evenly. Bake until it sets, about 22 to 25 minutes; do not over bake. Surface should be light golden yellow, very slightly firm on top.
5. Transfer pan to a rack and cool completely, about 25 to 30 minutes. Dust lightly with confectioners sugar, then cut into 24 squares. Store in an airtight container in refrigerator for up to three days, or freeze for up to one month.
Source: Hannaford fresh Magazine, May - June 2007