Found in a newspaper feed. Simple. Similar to lemon squares. I would avoid the food coloring altogether.
Ingredients
For Crust
1 cup flour
1/4 cup powdered sugar
1/4 teaspoon sea salt
1 stick unsalted butter, cold
For Creamy Lime Filling
2/3 cup fresh lime juice (about 6 limes)
1-1/4 cups sugar
1/4 cup flour
4 eggs
2 teaspoons lime zest
Green food coloring
Powdered sugar, for dusting
Instructions
1. Heat oven to 350 F.
2. For crust, combine the powdered sugar, flour and sea salt in a large bowl. Cut in the cold butter and work with your fingers until the mixture resembles cornmeal. Press into a greased 9-by-9-inch pan. Bake for 20 to 25 minutes, or until golden.
3. To make the filling, whisk together the granulated sugar and flour in a bowl. Add the eggs, one at a time, whisking well after each addition. Add the zest, lime juice and enough green food coloring to produce the desired color. (Be very careful not to add so much coloring you make your filling neon green.) Mix until everything is smooth and combined.
4. Pour filling over hot crust and return to oven to bake for 20 minutes or until filing no longer jiggles. Let cool completely in the pan before slicing and dusting with powdered sugar.