Slice the roast into 1/2 inch cubes. Dry off the cubes with paper towels. In a large Dutch oven, sear them in bacon grease. Lower the heat, stir in flour, cumin, chili powder, garlic, oregano, tomato and onions. Cover with water or beef stock. Stir the pot until well incorporated. Add the remainder of water or stock. Bring the liquids to a boil, cut the heat to a slow simmer and braise for 1 1/2 - 2 hours. Stir the pot - on occasion. Season to taste with salt - near the end of the cooking time. Garnish with lime wedges.