Preheat the oven to 350°F (175°C).
Line two baking sheets with parchment paper.
In a bowl, whisk together 1¾ cups flour, 2 tablespoons cocoa, 1½ teaspoons baking powder, and ½ teaspoon salt. Set aside.
In a large bowl, beat ½ cup softened unsalted butter with 1 cup granulated sugar until light and fluffy, about 2–3 minutes.
Beat in 2 large eggs one at a time, then add 1½ teaspoons vanilla. Mix in 1–1½ teaspoons red gel food coloring (or more liquid color) until vibrant.
Add the dry ingredients in two additions, alternating with 2 tablespoons buttermilk.
Mix just until combined. The dough should be soft, thick, and scoopable.
Let the dough rest for 10–15 minutes to firm slightly. Meanwhile, pour 1 cup powdered sugar into a shallow bowl.
For extra defined crinkles, mix in 1 tablespoon cornstarch.
Use a small cookie scoop (about 1 tablespoon). Roll dough into balls, then roll generously in powdered sugar until fully coated.
Arrange on the prepared sheets, spacing 2 inches apart. Bake for 10–12 minutes until the tops are cracked and the edges are set but centers are still soft.
Cool on the sheet for 5 minutes, then transfer to a wire rack to cool completely.
The cookies will continue to set as they cool.