1. Preheat oven to 350°.
2. Place butter and next 4 ingredients in a large bowl; beat with a mixer at medium speed until smooth.
3. Lightly spoon flour into dry measuring cups; level with a knife. Combine flour, baking powder, and salt in a bowl. Add flour mixture to butter mixture, stirring well. Fold in chocolate morsels and lime rind.
4. Press dough into an 8-inch square baking pan coated with cooking spray. Bake at 350° for 29 minutes or until a wooden pick inserted in center comes out clean. Cool completely in pan on a wire rack.