In a medium bowl, whisk together the flour, baking powder and salt; set aside.
In a large bowl, with a mixer, beat together the butter and sugar until smooth and creamy. Add the eggs and vanilla and beat again.
Add the dry ingredients to the wet ingredients and mix just until no more streaks of flour remain.
Divide the dough in half. Add ¼ teaspoon of orange food coloring to one half and ¼ teaspoon of black food coloring to the other half. Knead each portion until the color is evenly distributed.
Roll out the black dough on a sheet of parchment paper into a 9x15 inch rectangle. Transfer it to a baking sheet and set aside.
Roll out the orange dough on another sheet of parchment paper into a 9x15 inch rectangle.
Carefully place the parchment paper with the orange dough on top of the black dough, aligning the edges as best as you can. Chill the layered dough in the fridge for 20 minutes.
Remove the dough from the fridge. Peel off the top layer of parchment paper from the orange dough and lay the orange layer on top of the black layer.
Trim the edges to make a clean rectangle. Starting from the shorter side, roll the dough tightly into a log. Apply gentle pressure to ensure the layers stick together.
Wrap the rolled dough log in wax paper and refrigerate it for at least 2 hours.
Preheat your oven to 350°F (180°C), or 160°C for a fan oven, and line a baking sheet with parchment paper.
Unwrap the chilled dough and place it on a cutting board. Slice the dough into ¼ inch thick slices using a sharp knife.
Place the cookie slices on the prepared baking sheet. Bake for 10 minutes or until the edges are set.
Remove the cookies from the oven and let them cool on the baking sheet for 1-2 minutes before transferring them to a wire rack to cool completely.
Notes
Chilling the dough is a MUST. If you don't, the dough won't stick together properly, and the cookies won't turn out.
If you want to add a topping, a little bit of powdered sugar or a light glaze is never a bad idea. Just make sure that whatever topping you add is light so that it doesn't overpower those orange and black colors.
I highly recommend using gel food coloring. Gel food colorings add really bright colors and do a great job of coloring the dough evenly and easily. They also don't alter the flavor or the texture of the cookies. We used orange and black gel food coloring, but you could also use other Halloween colors like purple and green or even candy corn colors. Whatever the party decor is, match it to the colors of these pinwheel cookies.
Make sure to make an even amount of black and orange dough. It can be hard to eyeball it and get an accurate measurement, so if you want to use a scale to weigh the two balls of dough so that they're an even weight before adding the gel food coloring to them, this would be the best way to do so.
Roll the dough in sprinkles and sugar. You can add some extra sweetness to these Halloween party cookies by rolling the cookie dough log before you slice it and bake it. Halloween sprinkles are so much fun!