"Hey guys! I'm vegan! Did you know I'm vegan? Have I said that I'm vegan already? Read my sign, it says VEGAN, it's in all caps so you know just how VEGAN I am."
actually asking out of curiosity. Is it not vegan because of butter or because of eggs? Both ingridients seem equally non-vegan to me. So how do you make your cake, or any pastry without any of them? Or maybe you don't eat cakes because they are non-vegan by definition? And what's your views on using yeast?
Sorry, vegan ideology is quite foreign for me, geographically speaking, therefore mostly unknown
The cake isn't vegan because of both the ingredients you listed, there are tonnes of recipes that don't use animal products. If you live in a country that had to ration during the world wars, you might even have a family recipe that's vegan. If you look up "Chocolate Depression cake" (Depression as in "the great depression", not referring to mental health), you'll find some options.