Preheat the oven to 350 degrees Farenheight. Grease and flour three 7-inch round cake pans (or, one 13 x 9-inch baking dish).
In a large bowl, whisk together the sugar, flour, cocoa powder, salt, baking powder, and baking soda.
In a medium bowl, whisk together the eggs, milk, vanilla, oil and tahini.
Add the wet ingredients to the dry ingredients and stir to combine.
Whisk in the boiling water.
Divide batter evenly between cake pans and bake until a toothpick inserted into the center comes out clean, about 23-25 minutes.
Let cakes cool completely before frosting.