Preheat the oven to 350 degrees. Grease a 10- or 12-cup Bundt pan.
In a mixing bowl cream together the butter and sugar until light and fluffy. Add the eggs one at a time and mix until combined. Add in the vanilla.
In a medium bowl, whisk the flour,baking powder, baking soda and salt.
Alternate adding the flour mixture and buttermilk to the butter mixture until everything is combined. Scrape the bowl well to be sure the batter is well combined.
Pour the batter into the bundt pan and spread evenly. Bake until a toothpick inserted into the cake comes out clean, 45 to 55 minutes.
Let the cake cool in the pan for 15 minutes, then flip the pan onto a cooling rack to cool completely.
Mix together the powdered sugar, vanilla extract and food coloring. Whisk until smooth, adding hot water 1 teaspoon at a time until desired consistency is reached. Pour over the top of the cake, trying to get a smooth, coated finish. Sprinkle with jimmies. Enjoy!