These cookies are dead simple to make but they taste special. And you can make the dough well in advance and freeze it. Even the baked cookies freeze well. I love a recipe that can be prepped ahead.
Technique tip: It's easier to keep slice and bake cookies square as you slice them than it is to keep them round. That's why these are shaped into square logs and frozen before slicing.
In a large bowl, with an electric mixer on medium, beat butter and sugar until combined and fluffy, about 3 minutes. Add egg yolks, lemon zest and lime zest, and beat until combined. Beat in flour, tea, baking powder and salt.2.
Divide the dough in half. Tip each half out onto a sheet of plastic wrap and shape into a 1¾-inch square cylinder. Freeze cylinders until solid, at least 4 hours.3.
Preheat oven to 350 F. Line two rimmed baking sheets with parchment.4.
Using a sharp knife, cut 1/4-inch slices from one frozen dough cylinder. Place slices on prepared sheets and bake until set and light golden around the edges, about 15 minutes, rotating the sheets halfway through.5.
Transfer the cookies to a rack and let cool completely. Repeat with remaining dough. Keep cookies in an airtight container at room temperature for 3 days or in the freezer for up to 2 months.