Preheat the oven to 350-degrees. In a bowl, whisk together flour, cocoa, baking powder, baking soda, and salt. Set aside.
In another small bowl, whisk together yogurt, water, and vanilla. Set aside.
Cream together butter and sugar. Until light and fluffy, about 3 minutes. Add eggs one at a time.
Alternate dry and wet. Add half of the flour mixture to the butter. Add the yogurt mixture, and add the remaining flour.
Mix until just combined. Line a loaf pan with parchment paper and spray with cooking spray.
Bake for 1 hour. Cool in the pan for 15 minutes. Turn out and cool completely.
Make the glaze! Whisk together powdered sugar, cocoa, water, and vanilla until smooth. Pour over cooled cake.
Decadent and divine.