This is a Shape Magazine recipe I found. I baked these this morning and couldn't wait until tonight to try them. Really tasty and only about 150 cal per square.
For the shortbread:
1/2 c slivered almonds
1/2 c flour
1/4 c powdered sugar
1/4 tsp salt
4 tbsp unsalted butter, cut into 8 chunks
For the filling:
1 c sugar
1/4 c flour
2 tsp grated lemon zest
1 tsp grated lime zest
1/4 c each lemon and lime juice
Preheat oven to 325 degrees and grease square 8x8 cooking pan. To make the shortbread, put the almonds in a food processor and process for 30 seconds or until coarsly ground. Add flour, powdered sugar, and salt and pulse 5 times until mixed. Add butter and process for 10-15 seconds or until no large chunks remain and the mixture is loose and sandy. Press into the bottom of cooking pan and bake for 22-24 minutes or until edges are lightly browned.
While the crust is baking, make the filling. Combine sugar and flour in a large bowl. Add lemon and lime zest, as well as lemon and lime juice. Add eggs and whisk mixture until smooth. Pour filling over crust and return to the oven and bake an additional 30 minutes or until center is set. Cool completely on a wire rack. Sift powdered sugar over squares and garnish with lime before serving. You can also keep refrigerated for up to a day before serving.