Preheat your oven to 200°F (93°C) and line a baking sheet with parchment paper.

In a clean mixing bowl, beat room temperature egg whites on medium speed until frothy (about 2 minutes).

Add cream of tartar to frothy egg whites and beat on high until soft peaks form (3 to 5 minutes).

Gradually add sugar, one tablespoon at a time, beating until stiff peaks form (4 to 6 minutes).

Gently sift cocoa powder and vanilla into the whipped mixture and carefully fold until just combined.

Transfer the meringue mixture into a piping bag and pipe small mounds on the baking sheet.

Bake for approximately 1 hour until dry and crisp to the touch.

Turn off the oven, crack the door, and allow the cookies to cool completely inside.