Preheat the oven to 350ºF (180ºC). Line two 9-inch (23-cm) round cake pans with parchment paper. Lightly grease with baking spray with flour.
In a large bowl, combine the flour, baking powder, baking soda, cocoa, and salt. Reserve.
Stir together hot water and instant coffee power until the coffee is dissolved. Reserve.
Using an electric hand mixer or a stand mixer, beat butter until creamy on medium-high speed, about 3 – 4 minutes. Add the sugar and beat on high speed for 4 minutes until creamed and pale, scraping down the sides and bottom of the bowl with a rubber spatula as needed. Then add sour cream, oil, vanilla, vinegar, and coffee; continue beating to combine, about 1 minute.
Turn the mixer to low and add the flour mixture in three batches, alternating with buttermilk, beginning and ending with the flour mixture; beat until just combined, about 30 – 45 seconds. Do not overmix.
Pour batter into prepared pan(s).
Bake for 30 – 40 minutes, or until a toothpick or cake tester inserted in the center of the chocolate cake comes out clean.
Remove the cakes from the oven. Let the cakes cool in their pans on wire racks for 10 minutes before removing them from the pans. Allow the cakes to cool completely, right-side up, on a wire rack before removing the parchment paper.