This is a basic shortbread recipe I just added lime to and really liked the flavor. A pastry blender works great when you are trying to incorporate flour into butter. This one was my grandmothers, the newer ones have a place for your thumb which helps if your mixture is thicker.
1 c butter, softened
1/2 c sugar
zest of 2-3 limes
with pastry wire blend them together
2 1/2 c flour
then blend in flour till crumbly, turn onto saran wrap and press together
Press into shortbread pan or baking dish till about 1/2 inch deep, then score the dough to the shapes you want to cut the cookies into.
I used round cake pan and this recipe filled 2 cake pans.
bake at 325 for 20 min or just starting to brown on edges