In the bowl of a stand mixer, cream the butter & sugar together until whipped and fluffy. Add the extract, milk, & eggs. Beat until evenly combined and the batter's smooth.
To a large mixing bowl, add the flour, cocoa powder, baking soda, & salt. Using a whisk or fork, stir together until all ingredients are evenly combined.
Set the mixture to a slow speed, and steadily, but slowly, add the dry mixture in- mixing just until the batter comes together and is evenly combined.
Add the hot water, mixing again just until evenly combined.
Spray 2 9" round cake pans liberally with cooking spray. Pour the batter into them, dividing evenly between the two. Give each pan a wack onto the counter 2-3 times to get any trapped air bubbles out and to make sure the batter's even.
Bake the cakes at 350 degrees for 20 minutes, or until a toothpick inserted in the center comes out clean.
Remove the cakes from the oven, and set them aside from heat to cool in the pans for 5 minutes. Run a butter knife along the outer edges to release, then carefully turn the cakes out onto cooling racks to finish cooling completely.