Preheat the oven to 350°F.
Lightly oil 8 -inch round cake pan.
In a large bowl, sift together the flour, sugar, baking soda, salt, and cocoa powder.
In another bowl, whisk together the oil, buttermilk, eggs, food coloring, vinegar, and vanilla.
Mix the dry ingredients into the wet.
Pour the batter into prepared 20 cm round cake pan.
Bake in preheated oven for 70-80 minutes, or until a toothpick inserted into the center of the cakes comes out clean. (After 50 minutes of baking I covered the cake with aluminum cake, to prevent the top from burning).
Remove from the oven and let cool completely.