Preheat the oven to 425°F (220°C). Toss the potato slices with olive oil, onion powder, garlic powder, chili powder, cayenne pepper (if using), salt, and black pepper.
Spread the seasoned potatoes evenly on a baking sheet and roast for 45 minutes, flipping them halfway through cooking for even crispiness.
In a large skillet, cook the ground beef with the finely chopped yellow onion until the meat is browned. Drain excess fat.
Stir in the taco seasoning and 1/2 to 1 cup of water or beef broth. Simmer the mixture until it thickens.
For the cheese sauce, melt the unsalted butter in a saucepan. Whisk in the flour, salt, black pepper, and chili powder to form a roux.
Gradually add the whole milk, whisking continuously until smooth and thickened.
Remove from heat and stir in the grated cheddar cheese until fully melted and creamy.
Assemble the bowls by layering roasted potatoes, taco meat, and cheese sauce.
Top each bowl with diced Roma tomato, chopped cilantro, reserved chopped onion, a squeeze of lime juice, and your favorite hot sauce.
Add optional toppings such as sour cream or Greek yogurt, sliced jalapeños, avocado, or guacamole as desired.