Start by gathering all the ingredients. Pre-slice your onion bun, pickled onions, and roast beef. Having everything organized makes the cooking process seamless.

Lightly toast your onion sandwich bun in a toaster or on a skillet. A little crispness adds an enjoyable texture and prevents it from getting soggy.

In a pan over medium heat, gently warm the sliced roast beef until heated through. This step brings out the flavors and makes the beef even more tender.

While the beef warms, combine the cheddar cheese sauce and Country French dressing in a small bowl. Mix until they’re well-blended. This sauce concoction is where things start to get interesting.

Now, for the fun part! Start with your toasted bun. Spread the Dijon mustard on the bottom half. Layer on the warm roast beef, followed by a generous drizzle of your cheddar dressing mix. Finally, top with the pickled red onions and the top half of the bun.

Your homemade Beef and Cheddar is ready to be devoured! Serve it with those curly fries or coleslaw on the side for a complete meal. Dig in and savor every bite.