Preheat oven to 350 F.
Grease a 10-12 cup bundt pan and dust lightly with cocoa powder.
In a small pot, melt the butter. Add the water and salt and set aside.
In a large bowl, whisk the flour, cocoa powder, sugar, and baking soda.
Whisk in the butter mixture, until smooth.
Whisk in the eggs, one at a time.
Whisk in the yogurt and vanilla extract.
Scrape the batter evenly into the bundt pan.
Bake for 45 minutes, or until a skewer inserted into the centre of the cake comes out clean.
Remove from oven and let cool for 20 minutes on a wire rack.
Invert onto a rack and let cool completely.