In a large mixing bowl, stir together the cake and pudding mixes. Add the milk and water and stir to combine. Beat in the eggs one at a time, combing well after each, then add the butter and vanilla extracts. Beat for 6 minutes at high speed.
Place a rack in the center of your oven and preheat the oven to 350 degrees F. Grease and flour a large (10 or 12-cup) bundt pan and set aside.