Cake: Preheat oven to 350. Line bottoms of two greased 9 inch round baking pans with parchment paper, grease paper also. Divide marshmallows between pans. In a large bowl, whisk flour, sugar and baking soda. In a small saucepan, combine the butter, cola and cocoa; bring just to a boil stirring occasionally. Add to flour mixture, stirring just until moistened.
In a small bowl, whisk eggs, buttermilk and vanilla until blended; add to the flour mixture, whisking constantly. Pour into the prepared pans, dividing batter evenly. Marshmallows will float to the top, that's ok.
Bake 25 to 30 minutes, test at 25 according to your own oven. Cool in pans for 15 minutes before removing to wire racks, remove parchment paper, cool completely.
Frosting: In a small bowl, beat butter, confectioners sugar until smooth. Beat in marshmallow crème and juice on low speed just until blended. Place on cake layer on serving plate, spread frosting in middle, top with remaining layer, frost the rest of the cake and sides also. Top with cherries for decoration if you desire.