In a larger skillet over medium-high heat, combine ground beef and onion. When slightly browned drain the grease. Return to heat and add onion, chili powder, salt and pepper to taste. Cook until completely browned.
In a medium size sauce pan over medium heat, melt the butter. After the butter has melted add the flour. Whisk until a paste. Add the milk and continue to whisk.
Adjust the sauce heat to high and bring to a boil. Immediately return the heat to a simmer. Add cayenne pepper, and salt and pepper to taste. Combine cheeses and gently stir until melted and an even consistency.
Cook your hotdogs using your favorite method. Grilling, boiling, or even the microwave. Or use the same skillet after cooking the ground beef to save on cleanup.
Build your Nacho Dog Tacos with Taco Tenders on a paper plate to catch your cheesy drippings! Enjoy while watching a ballgame on the couch!