I am a firm believer that sandwiches belong at the dinner table…are you with me? Well, this roast beef sandwich absolutely fits that category. She’s big, she’s bold, she’s messy…and she is insanely DE-lish.

I start by searing and slow-roasting the beef in a cast iron pan until it’s incredibly tender. Then, in the same pan, I quickly sauté onions to capture all those flavorful browned bits. A creamy horseradish mayo ties everything together, bringing just the right amount of bite.

To build the sandwich, I pile everything onto a soft Kaiser roll: first the medium-rare slices of beef, then the glossy caramelized onions, a generous smear of horseradish mayo, and finally a slice of my favorite Grillo’s pickles. The pickle is key…it cuts right through the rich, savory layers.

This is not a dainty sandwich, but my goodness…is it delicious.

Ingredients:

Boneless Beef Roast (Top Round or Top Sirloin) – A lean, flavorful cut that becomes incredibly tender when roasted slowly. Perfect for slicing thin and piling high on sandwiches.

Onion Powder – Provides a savory backbone of flavor that complements the caramelized onions later in the sandwich.

Dried Thyme – A classic herb pairing with beef that brings a warm, earthy note.

Avocado or Grapeseed Oil – A neutral, high-heat oil used to coat the roast before seasoning and roasting.

Mayonnaise – The creamy base for the horseradish sauce that ties the entire sandwich together.

Prepared Horseradish – Adds a sharp, peppery kick that cuts through the richness of the beef.

Yellow or Red Onions – Slowly sautéed until soft and deeply caramelized, adding sweetness and incredible depth of flavor.

Kaiser Sandwich Rolls – Soft yet sturdy rolls that hold up beautifully to the juicy beef and toppings.

Dill Pickle Slices (Grillo’s Recommended) – Bright, crunchy, and acidic, they cut through the richness of the sandwich and bring the whole thing into balance.

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How to make my Roast Beef Sandwiches:

• Remove the beef from the fridge an hour before cooking so it reaches room temperature.
•  Pat dry with a paper towel and rub all over with oil. Season all over with 3 teaspoons of salt, 1 teaspoon dried thyme, 1 teaspoon onion powder, and ½ teaspoonfresh cracked pepper. Set aside for an hour at room temperature.
• Preheat the oven to 325 F. 

• Transfer the seasoned beef to a cast iron pan, fat side up, and roast for about an hour or until the internal temperature reads 135 for medium rare (that’s how we like it cooked). 

• Remove the beef from the oven when done, using tongs to set the beef on a cutting board to rest for at least 20 minutes to allow the juices to redistribute.

• Without wiping out the pan, bring the same pan you cooked the beef in to warm back up over medium heat. 

• Add the sliced onion and a big pinch of salt to the pan and cook, stirring periodically, for 15-20 minutes. Halfway through, add a splash of water to the pan and use a wooden spoon to scrape up any bits leftover from the beef… don’t leave that flavor behind!

• When the onions are done they will be soft and deeply browned from the pan’s seasoning. Remove from the heat.

• While the beef rests, whisk the horseradish and mayonnaise in a small bowl and set aside for serving.

• Assemble the sandwiches by spreading a generous layer of horseradish mayonnaise over bread roll bottoms. Add a big scoop of sautéed onions before dividing the sliced roast beef and start to build, evenly on the onions. Add a Grillo pickle on top of the beef, close the sandwiches and serve. 
• This is a big sandwich, so I suggest cutting these in half (not because you won’t want to eat the whole thing, but it’ll be less messy!)

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