Pre-heat oven to 350°F.
Grease two 9-inch cake pans; line the bottoms of the pans with a parchment round; butter the parchment paper; flour the pans.
Using an electric mixer, on medium-high speed, cream the butter and sugar until light and fluffy; about 3 minutes.
Turn the mixer to high and add the eggs, one at a time, mixing for about a minute after each addition; scrape down the bowl and beat until well incorporated.
In a separate small bowl, mix together the cocoa powder, vanilla extract and red food coloring to make a thick paste.
Add to the batter and mix, on medium speed, until completely combined.
You may need to stop the mixer to scrape the bottom of the bowl, making sure that all the batter gets color.
Reduce the mixer speed to low and slowly add half of the buttermilk; add half of the flour and mix until combined.
Scrape the bowl and repeat the process with the remaining buttermilk and flour; beat on high until smooth.
Again, reduce the mixer speed to low and add the salt, baking soda and vinegar.
Turn to high and beat for another couple of minutes until completely combined and smooth.
Divide the batter evenly between the two cake pans; place in the pre-heated oven and bake for about 30 minutes, or until a thin knife or skewer inserted into the center comes out clean.
Remove from the oven and cool for 10 minutes; then remove cakes from the pans and place on a cooling rack to cool completely.