Preheat the oven to 350.

In a separate bowl, whisk together flour, cream of tartar, baking soda, and salt. Set the bowl aside.

Using a stand mixer with the paddle attachment, cream butter and 1.5 c sugar together.

Continue mixing and add eggs to the creamed butter & sugar one at a time.

Gradually add in the dry flour mixture to the wet ingredients, mixing between additions.

Once you've prepared the dough, split dough up into 4 additional bowls (leaving some still in the mixing bowl so you have some dough left that doesn't have any food coloring on it).

In the four bowls with dough, add in the food coloring to reach the hues you're looking for - probably 2-4 drops of a color in each bowl. For these cookies, I had one bowl with red dough, one bowl with yellow, one with orange (I mixed a drop of the red food coloring with a few drops of yellow), and one brown (where I mixed red, yellow, and green together). Mix each bowl up until the food coloring is thoroughly blended into the dough.

In a separate shallow bowl, mix the remaining 1/4 c sugar + 3 tsp of cinnamon and set aside.

Take small pinches of each dough color and begin to roll them together to form a dough ball - about an inch or so wide. Roll the dough in the cinnamon + sugar mixture in the shallow bowl.

Once you've got a sugar/cinnamon-coated dough ball, gently press the dough onto a non-stick baking pan (see my notes for the BEST ones to use for this), and repeat this process until you've used up all the dough, pressing each dough ball into the next to form one large pan of marbled cookie dough (see photos for details!).

After you've used all the dough and pressed it onto the pan, use your fingers to blend seams between flattened dough - nothing too technical!

Sprinkle remaining cinnamon and sugar over the top of the dough (if you don't have anymore, just whip up a little more to sprinkle on top), and place in preheated oven.

Bake the dough for 10-12 minutes, and remove from the oven. **You don't want the cookies to be crispy, but you also don't want them to be way too soft, so check the dough before you officially remove it from the oven.** (You're going to allow the freshly baked cookie to sit out of the oven for about 10 minutes before you begin cutting the cookies.)

Set the pan aside to begin cooling, and in the meantime, whip up the buttercream frosting by mixing together the butter, powdered sugar, and vanilla. Add a tiny splash of milk if you need it, but you don't want the icing to be too runny! Set the frosting aside until you're ready to use it.

After the dough has cooled for about 10 minutes out of the oven, start using your leaf-shaped cookie cutters to press into the dough and set on a cooling rack. I recommend metal cookie cutters for this - not plastic ones! Repeat this process until you've run out of large cookie to cut out! Try to cut the leaves close together so you use up as much of the dough for the leaf shapes as you can.

The number of cookies you get out of this dough will depend on the size of your cookie cutter, but I got about 15-20 large leaf cookies from this amount of dough.

Once you've cut out all the cookies and allowed them to cool on the cooling rack, put your buttercream frosting into a Ziplock bag or other type of sandwich bag, cut a small hole in one of the corners of the bag, and begin piping the leaf veins onto each cookie.

Optional: sprinkle on some cinnamon & sugar over the leaf veins if you want them to be a little more brown and a little less white.

Enjoy!