Kitchen notes · a little help before you start
Roast Beef Sandwich with Melted Cheese and Caramelized Onions
Sweet caramelized onions and melted cheese make thinly sliced roast beef feel especially generous in this warm sandwich. The bread holds the soft filling together, with a little browned onion in each bite alongside the savory beef.
- Prep
- 10 min
- Cook
- 20 min
- Total
- 30 min
- Original yield
- Serves 4
- Ingredients
- 7 listed
Make it part of your week
Recipe categories & planning details
- Meal type
- Lunch
- Primary protein
- Beef
- Cuisine
- American
- Cooking method
- Roasting · Baked & roasted
- Preparation & total time
- Prep: 15 minutes or less · Total: 30 minutes or less
- Dish type
- Sandwiches
A few quick notes
1. Give the onions their time
Keep the skillet at medium-low and let the onion rings cook until they’re lightly browned. Turning them now and then helps them soften evenly without pushing them too far.
2. Use cooked roast beef
The beef goes onto the bread already cooked and thinly sliced. The broiler is just there to melt the cheese, so don’t count on it to cook or warm a thick piece of meat through.
3. Watch the broiler closely
The cheese only needs a minute or two under the broiler. Stay nearby, because the bread and cheese can go from nicely melted to scorched fast.
Get to know the ingredients
White onion
Slice the onion into rings before it hits the skillet. Rings give you good coverage on each sandwich and are easy to divide over the roast beef once they’ve browned.
Leftover roast beef
Thin slices work best here because each sandwich gets a measured layer of cooked beef before the onions and cheese go on top.
Swiss or provolone
Use either reduced-fat Swiss or provolone. Both go on top of the onions, where the broiler can melt the cheese over the filling instead of hiding it underneath.
Let’s make it
Choose your servings, then check things off as you go.
Original recipe: Serves 4. Original quantities shown.
Check ingredients as you prepare them. These checks stay on this page.
How to make it
0 of 4 steps completeMake room for Roast Beef Sandwich with Melted Cheese and Caramelized Onions
Review ingredients in your pantry before anything is added. Meal plans use your household size; grocery-only additions use the servings selected above.
The last little job
Melt, then pull it out
Finish the sandwiches under the broiler just until the cheese melts. Keep an eye on them the whole time, especially near the end, so the bread doesn’t burn.
A little more help as you go
Build each sandwich evenly
After opening the bread, add the cooked roast beef first, then divide the caramelized onions over the top. That order keeps the onions under the cheese, where they’ll stay put better as it melts.
Season the onions in the pan
Add the salt and pepper to the onions while they cook, before assembling the sandwiches.
A few questions you might have
Should the onions be dark and jammy?
No, they’re cooked until slightly brown. Keep the heat at medium-low and turn them occasionally so they soften and pick up color without burning.
Do I need to heat the roast beef in the skillet first?
No. The cooked, sliced roast beef is placed straight on the bread, then topped with onions and cheese before broiling.
Which cheese should I choose?
Either reduced-fat Swiss or provolone works here. Use the one you prefer, then broil briefly until it melts over the onions and beef.
How do I divide the sandwich fillings?
Each piece of bread gets cooked roast beef, then a quarter of the caramelized onions and cheese on top before broiling.
Why cut the bread before broiling?
The bread is sliced open before the beef, onions, and cheese go on. That gives the toppings a flat surface and lets the cheese melt directly over the filling.
Any more cooking tips?
Makes 4 sandwiches, each have 2 oz bread, 3 oz roast beef, 1 oz cheese and 1/4 of the onions.
Storage & reheating safety
For cooked, perishable leftovers, refrigerate within 2 hours (1 hour above 90°F), using shallow containers for prompt cooling. Keep the refrigerator at 40°F or below, use refrigerated leftovers within 3–4 days, and reheat hot leftovers to 165°F, checked with a food thermometer. Follow any shorter package limit.
These are general safety limits, not a tested storage or freezing recommendation for this particular dish. USDA leftovers guidance · Safe cooking temperatures
Recipe source: skinnytaste.com. Ingredient names and quantities may be adapted for the pantry.
Preparation notes follow the recipe shown here.