Whip Egg Whites
Adjust oven rack to lower-middle position and heat oven to 325 F. With electric mixer fitted with whisk attachment, whip egg whites and cream of tartar on medium-high speed until soft peaks form, about 2 minutes. With mixer running, slowly add 2 tablespoons sugar and whip until just stiff and glossy, about 1 minute; set aside.
Combine flour, remaining sugar, baking powder and salt in large bowl. Whisk water, oil, egg yolks and vanilla in medium bowl until smooth. Whisk wet mixture into flour mixture until smooth. Whisk one-third whipped egg whites into batter, then gently fold in remaining whites, 1 scoop at a time, until well combined. Scrape mixture into 16-cup ungreased tube pan.
Bake until toothpick inserted into center comes out clean and cracks in cake appear dry, 55 to 65 minutes. Cool, inverted, to room temperature, about 3 hours. Unmold and serve.