2/3 cup butter, softened
1/2 cup packed brown sugar
2-1/2 cups all-purpose flour, divided
4 tsp. finely shredded lemon peel, divided
2-1/4 cups granulated sugar
1/2 cup lemon juice
3/4 tsp. baking powder
1/8 tsp. ground nutmeg
1 tsp. finely shredded lime peel
2 Tbsp. sifted powdered sugar
1. Prepare Candied Citrus Slices or Strips, (see recipe), if desired. Preheat oven to 350 degrees F. Line a 13x9x2-inch baking pan with heavy foil; set aside.
2. For crust, in large mixing bowl beat butter on medium to high 30 seconds. Add brown sugar; beat until combined. Beat in 2 cups of the flour until crumbly. Stir in 2 teaspoons of the lemon peel. Evenly press on bottom of prepared pan. Bake 20 minutes.
3. Meanwhile, for filling, in medium bowl combine eggs, granulated sugar, remaining 1/2 cup flour, lemon juice, baking powder, and nutmeg. Beat on medium 2 minutes. Stir in remaining lemon peel and the lime peel. Pour over hot crust. Bake 20 minutes more or until edges are browned and center appears set. Remove to rack; cool 1 hour. Refrigerate, covered, 2 hours.
4. To serve, sprinkle evenly with powdered sugar. Lift from pan using foil; cut into bars. Add Candied Citrus Slices or Strips, if desired. Store, covered, in refrigerator up to 3 days. Makes 16 to 20 bars.
5. Candied Citrus Slices: In large skillet combine 1/4 cup water and 3/4 cup sugar; bring to boiling. Add 2 lemons or 10 key limes, thinly sliced. Simmer gently, uncovered, for 1 to 2 minutes or until just softened. Transfer to rack; cool.
6. Candied Citrus Strips: Cut strips of peel from 2 lemons or 2 limes. With spoon scrape away white pith. Cut into thin strips and cook in sugar mixture as above.