Roast Beef Sandwiches with Caramelized Onion

Elevate your sandwich game with these irresistible Roast Beef Sandwiches with Caramelized Onion—a gourmet treat that's easy enough for a weeknight meal yet impressive enough for entertaining. Tender, thinly sliced roast beef is warmed to perfection and layered with sweet, golden-brown caramelized onions, which are cooked slowly with butter, olive oil, and a touch of brown sugar for an indulgently rich flavor. A crisp toasted baguette forms the base, while a creamy blend of whole-grain mustard and mayonnaise adds a tangy twist. Optional additions like melted Swiss cheese and peppery arugula provide customizable flair. Ready in under an hour, this hearty sandwich is ideal for lunch, dinner, or any occasion that calls for comforting sophistication.

Nutriscore Rating: 62/100

Prep Time:15 mins

Cook Time:30 mins

Total Time:45 mins

Servings: 4

Ingredients

• 2 tablespoons unsalted butter
• 1 tablespoon olive oil
• 2 large yellow onions
• 0.5 teaspoon salt
• 0.25 teaspoon black pepper
• 1 teaspoon brown sugar
• 1 large baguette
• 0.75 pound roast beef (sliced thin)
• 4 slices Swiss cheese (optional)
• 3 tablespoons whole-grain mustard
• 3 tablespoons mayonnaise
• 1 cup arugula (optional)

Directions

Step 1

Peel and thinly slice the onions.

Step 2

In a large skillet, heat butter and olive oil over medium heat.

Step 3

Add the onions, salt, and pepper to the skillet and stir to combine.

Step 4

Cook the onions, stirring occasionally, for 20-25 minutes, or until they become soft and golden brown. If they start to stick, add a splash of water to the skillet.

Step 5

In the last 5 minutes of cooking, stir in the brown sugar to enhance the sweetness of the onions.

Step 6

While the onions are caramelizing, preheat your oven to 375°F (190°C) and slice the baguette into four equal portions.

Step 7

Split each portion of the baguette lengthwise and toast them in the oven for 5-7 minutes, or until lightly crisped.

Step 8

In a small bowl, mix the whole-grain mustard and mayonnaise until well combined. Spread the mixture evenly on the inside of each toasted baguette piece.

Step 9

Heat the sliced roast beef briefly in the skillet to warm it up, about 2-3 minutes.

Step 10

Layer the warmed roast beef onto the bottom half of each baguette.

Step 11

Top the roast beef with caramelized onions and a slice of Swiss cheese, if using.

Step 12

Place the sandwiches under the oven broiler for 1-2 minutes, just enough to melt the cheese.

Step 13

Add a handful of arugula on top, if desired, and close the sandwich with the top half of the baguette.

Step 14

Serve warm and enjoy your roast beef sandwiches with caramelized onions!

Nutrition Facts

Serving size	(1240.7g)

Amount per serving	% Daily Value*
Calories	2747.7

Total Fat 137.1g	0%
Saturated Fat 49.0g	0%
Polyunsaturated Fat 1.3g
Cholesterol 447.1mg	0%
Sodium 5995.4mg	0%
Total Carbohydrate 216.3g	0%
Dietary Fiber 14.6g	0%
Total Sugars 32.1g
Protein 164.8g	0%

Vitamin D 24IU	0%
Calcium 1340.4mg	0%
Iron 23.4mg	0%
Potassium 2253.7mg	0%

*The % Daily Value tells you how much a nutrient in a serving of food contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.

Source of Calories

Fat: 44.7%

Protein: 23.9%

Carbs: 31.4%