Preheat the oven to 350°F. Spray two 8-inch round cake pans with nonstick cooking spray and line each with parchment paper.
In the bowl of a stand mixer with a paddle attachment, mix together the flour, sugar, cocoa powder, baking soda, baking powder, and salt.
In a separate bowl, combine the buttermilk, oil, eggs, and vanilla.
With the stand mixer on low speed, slowly add the wet ingredients to the dry. With mixer still on low, add the coffee and mix just to combine. Scrape the bottom of the bowl with a rubber spatula.
Arrange 14 Oreo cookies on the bottom of each cake pan.
Evenly divide the batter between the prepared pans and bake for 35-40 minutes, or until a cake tester comes out clean. Some Oreos will rise up into the batter and that is okay!
When done, remove the cakes from the oven. Let them cool in the pans for 30 minutes; then turn them out onto a cooling rack to cool completely.
Store the cooled cakes in the refrigerator until ready for assembly.