In a large bowl, combine cocoa powder, sugar, and oil. Beat with a mixer until shiny and smooth.
Add eggs one at a time, mixing well after each addition. Stir in vanilla extract.
In a separate bowl, whisk together flour, baking powder, and salt.
Gradually add dry ingredients to the wet mixture, mixing just until combined.
Cover dough with plastic wrap and refrigerate for at least 4 hours or overnight.
Preheat oven to 350°F. Line baking sheets with parchment paper.
Scoop chilled dough into 1-inch balls using a cookie scoop or tablespoon.
Roll each dough ball in powdered sugar until fully coated.
Place on baking sheet 2 inches apart and bake for 10–12 minutes, until edges are set and centers look slightly underbaked.
Cool on baking sheet for a few minutes, then transfer to a wire rack to cool completely.