Put the teabag in a small cup or ramekin. Add the 3 tablespoons boiling water and let the teabag steep for about 5 minutes. Use a spoon to press the remaining liquid from the teabag and discard the teabag. Let the tea sit and cool while you prepare the other ingredients.
Mix the salt, baking powder, and flour in a bowl and set aside.
In a mixing bowl, cream the butter and sugar until fluffy. Add the egg, vanilla extra, lemon zest, and tea.
Mix until incorporated then cover the mixing bowl with plastic wrap. Refrigerate for at least 2 hours or overnight.
Once you're ready to bake, preheat the oven to 350 F.
Use baking sheets or parchment paper to line two cookie sheets.
Put the ¼ cup white sugar in one shallow bowl, and the ¾ cup powdered sugar in another.
Use your hands to roll the dough into small balls, definitely no larger than a golf ball. Roll each ball in regular sugar first, then the powdered sugar.
Place on the lined cookie sheets and use your fingers to flatten slightly.
Bake for 12 minutes. Let cool on the cookie sheets for a few minutes and then cool completely on a wire rack.