1) In a large bowl, whisk together the buttermilk, egg, and sugar. Add the tomatoes and soak for 10 minutes, turning the tomatoes occasionally.
2) In a large bowl, whisk together the polenta, flour, salt, thyme, and cayenne. Season with pepper. Set aside.
3) Heat a large cast-iron skillet over medium-high heat. Lay the bacon in the skillet and cook, turning once, until crispy, about 2 minutes per side. Transfer the bacon to a paper towel to drain, reserve the bacon fat in the skillet. Pour the oil into skillet to a depth of 1-cm and heat until hot.
4) Drain the tomatoes and toss in the polenta mixture until well coated. Working in batches if needed, fry the coated tomatoes, turning once, until lightly browned and hot, about 3 minutes the first side, and 2 minutes the second side. Using a slotted spatula or spoon, transfer the tomatoes to a paper-towel lined plate to drain.
5) Arrange the fried tomatoes on a platter and crumble the bacon over the top. Serve immediately.