Hi from Washington, DC. This is easily one of the most vegan friendly cities we've been to, in the sense that so many non-vegan places have clearly labeled vegan options. Like this cupcake we found from Red Velvet Cupcakery, on 7th street.
They have two vegan cupcakes, the black velvet and the white velvet. I chose white velvet, which was soft and fluffy and vanilla-licious.