Undefeated on 129 overnight, Gautam scored a magnificent 257 off 394 balls with the help of 20 boundaries.
Replying to the Karnataka's mammoth score, Vidarbha reached 48 for no loss with openers Shiv Sundar Das (26) and Faiz Fazal (21) to resume tomorrow.
It was another day which was dominated by Gautam as he added 128 runs to his overnight score. He was ably supported by Manish Pandey (53) and Stuart Binny (85), who ripped the Vidarbha bowling apart.
Gautam was removed by part-time medium pacer Shalabh Srivastava, caught by wicketkeeper Amol Ubarhande.
Binny, who took the Vidarbha attack to sword, was caught by Shrikant Wagh off Srivastava after a knock of 85, which contained eight boundaries and two sixes.
While R Vinay Kumar was run out for one, Abhimanyu Mithun's useful 20-run knock ended when Gaurav Upadhayaya got him caught by Faiz Fazal.
Resuming on their overnight score of 308 for two, Karnataka added a quick-fire 151 runs losing two more wickets and were firmly in driver's seat as they went into lunch 459 for four at lunch.
Lokesh Rahul (157) was first to go when he was caught by Hemang Badani off Ravikumar Tahkur after adding twelve runs to his overnight score of 145.
Vidarbha bowlers, who were off-colour in last two sessions yesterday, managed to pick a couple of wickets but conceded far too many runs after Pandey and Binny ripped their bowling apart sharing 90 runs.
