In a large mixing bowl, cream butter and sugar until light and fluffy.
Add eggs and vanilla, beating until combined.
In a medium bowl, stir together flour, baking soda, and salt.
Add to the mixing bowl alternately with the buttermilk, beating until just combined.
Line two 9-inch round baking pans with parchment paper, and extend it slightly over the edge in two places, so that you can lift the coffee cake layer out of the pan easily after baking.
Divide the batter evenly among the cake pans.