Whip the softened butter together with the sugar, either with the paddle attachment on your mixer or a sturdy spoon and bowl.

Scrape down the horn of the bowl of the mixer periodically and mix until light and fluffy.

Crack the egg into a small bowl, and then add to the creamed butter and sugar mixture.

Mix well until fully incorporated and fluffy.

Add the vanilla, and either the citrus zest, or any other extracts, spices, or flavorings.

For best results, tint the dough mixture now if you are making pinwheel cookies (this will require making a separate batch of dough for each color).

Measure the flour into a medium mixing bowl.

Sift the baking powder and salt into the flour, and whisk or sift the dry ingredients until they are well combined.

Add the dry ingredients to the butter & sugar mixture.

Either stir and fold to mix, or pulse on low speed in your stand mixer until the mixture forms a stiff dough. Mix just until there are no pockets of dry ingredients. Don't overmix the dough.

If you are just making a small batch of cookies, divide and tint the dough after mixing, though you will get better results by making one batch of dough for each color as recommended above.

Wrap the dough tightly with plastic wrap, or place in airtight storage containers.

Chill the dough for 8-24 hours before rolling and shaping.

Line a clean work surface with a non-stick silicone baking mat or parchment paper. Dust this very lightly with flour if the dough is sticky at all.

Choose a color for the outside of the cookie log, and flatten it on the mat. Cover with a second non-stick baking mat or sheet of parchment or plastic wrap.

Roll out into a roughly 10"x14" rectangle. Carefully peel off the top layer of baking mat or wrap (chill briefly if the dough has softened to make it easier to work with). A bench scraper is helpful here! Set the rolled layer aside.

Repeat this process with the second layer. It's ok if these are a little messy looking (see photo). Just try to get thin, even layers that are roughly the same size.

Using the mat or parchment, pick up one sheet and lay the two dough-sides together. Gently roll over the top to press them together. If the dough is too soft or sticky to work, chill the layers briefly.

If you are doing a tri-color spiral cookie, repeat this process a third time.

Using the mat or parchment and a dough scraper to lift and compress the dough, working from the long side, roll up the layers into a log. Gently roll the log together under your palms to make it into a roughly even shape about 2" in diameter.

Try to press the layers together and roll the dough log tightly. Small air-gaps will fill in when the cookies bake, but large ones may leave hollow spots in your cookie spirals.

You can also roll the outside of the cookie logs in colored sugar or sprinkles for more sparkle.

If the dough is still cold, you can immediately slice and bake the cookies.

If you are working in a hot kitchen and the dough has warmed, chill the dough logs so that the cookies keep their shape when baked.

You can also wrap well and refrigerate or freeze the dough at this point (see below for tips).

Unwrap the cookie dough log and cut into 1/4" slices.

Place on a cookie sheet, with an inch or so between the cookies bake evenly. They will spread only a little. If you are baking one of the variations that uses less flour, leave more room between the cookies.