Preheat the oven to 350°F. Spritz a square 8 x 8 baking pan with baking spray or butter and flour. Sift together the flour, sugar, cocoa, baking soda and salt.
In a separate bowl, whisk together the eggs, vegetable oil, buttermilk, red food coloring, vinegar and vanilla.
Beat the wet ingredients gradually into the dry mixing just until combined.
Increase the speed of the mixer and beat for 1 minute until smooth.
Pour into the prepared pan.
Bounce the pan on the counter to remove trapped air bubbles and to settle the batter.
Bake for 30 minutes until the cake springs back when gently touched or a toothpick inserted into the center comes back clean. Do not over bake. Cool for 1 hour in the pan then carefully remove from the pan to a baking rack to cool completely.
To make the frosting: In a medium-size mixing bowl, beat together the softened cream cheese, butter, vanilla, salt and powdered sugar for 2 minutes or until smooth and creamy.
Frost the cake and sprinkle with toasted pecans. Cut into squares.