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