Add the olive oil to a cast iron skillet over medium heat. Once the oil is hot, add in the onions, thyme, oregano, and red pepper flakes and cook until the onions are soft and translucent, about 5 minutes. Add in the garlic and cook for 1 minute. Stir in the vodka and cook until the vodka is slightly reduced. Stir in the tomatoes, salt, and black pepper. Cover the skillet and place in the oven and cook for 1½ hours.