Bake the sliced potatoes at 425°F for 45 minutes, flipping every 15 minutes. Crank the heat to 450°F and bake another 10-15 minutes until brown and crispy.
In a skillet, cook the ground beef and ¾ of the yellow onion with the taco seasoning and 2 cups of water. Simmer until thickened.
In a saucepan, melt the butter and whisk in the flour. Cook for 1 minute, then whisk in the milk, salt, pepper, and chili powder. Simmer until thickened.
To assemble the bowls, layer the crispy potatoes, ground beef mixture, cheese sauce, remaining ¼ onion, diced tomato, cilantro, lime juice, sour cream, and Taco Bell sauce.
