Preheat the oven to 325 degrees F and grease a 9×13-inch baking dish.
In a large bowl, beat the cream cheese until smooth, then blend in the oil and sugar.
Add eggs one at a time, mixing well between additions, and then incorporate the vanilla.
In a small bowl, sift together the flour, baking powder, and salt. Gently fold these dry ingredients into the wet mixture just until combined. Gradually mix in the buttermilk until smooth.
Transfer the batter to the prepared baking dish and bake for 35-40 minutes or until an inserted toothpick comes out clean.
Allow the cake to cool completely while preparing the frosting.
In a large bowl, combine the cream cheese and butter until smooth. Gradually add powdered sugar and salt, mixing until fully combined.
Frost the cooled cake and refrigerate until ready to serve.
