Preheat your oven to 425°F (220°C). Toss the sliced russet potatoes in olive oil and season generously. Arrange them evenly on baking sheets, and roast for 45 minutes, flipping every 15 minutes. For extra crunch, crank up the oven to 450°F (230°C) and bake for an additional 10-15 minutes until golden brown and crispy.

In a skillet, sauté the ground beef with 3/4 of the chopped onion over medium heat until the meat is browned and the onion softens, about 8-10 minutes. Drain any excess grease.

Stir in the taco seasoning and add ½ to 1 cup of water or beef broth. Let it simmer on low for 5-7 minutes until the mixture thickens.

In a saucepan, melt the unsalted butter over medium heat. Whisk in the all-purpose flour, then gradually pour in the whole milk, whisking continuously until thickened, about 3-5 minutes. Stir in the shredded mild cheddar cheese until melted.

Start layering by dividing the crispy roasted potato slices into bowls. Top with the savory taco meat and drizzle with the cheese sauce.

Squeeze fresh lime juice over each bowl and sprinkle with diced Roma tomato, fresh cilantro, and any additional toppings desired.