Season the venison cutlets with salt and pepper to taste, then beat with a meat hammer to tenderize. Sprinkle while you pound the meat with a hammer until 1 cup of flour has been used.
Heat a little bit of the oil in a heavy skillet over medium heat. Cook until the onions are limp and turning golden-brown, about 10 minutes. Set the onions aside, and heat the remaining oil over medium-high heat. Brown the steaks on both sides in the hot oil.
Spread the onions over the browned venison steaks, then pour on the diced tomatoes. Cover, and bake in the preheated oven until the meat is tender, 45 to 50 minutes.
Remove the onion-topped steaks to a serving platter, and bring the pan juices to a boil. Dissolve 1 tablespoon of flour in 2 tablespoons of water and whisk into the pan juices to make a gravy. Boil about 5 minutes until thick and smooth. Pour the gravy over the steaks to serve.