This steak sandwich is loaded with juicy steak slices, melted Gruyère cheese, sweet caramelized onions, and the tastiest homemade spicy mayonnaise!
Whenever I have beef in the fridge, chances are good I’ll turn it into steak quesadillas, a patty melt, or a good old-fashioned steak sandwich. This time, I had skirt steak on hand, so I seared it, sliced it, and loaded it onto a baguette with melted cheese, caramelized onions, and homemade spicy mayonnaise. The crispy bread, juicy steak, and burst of flavors are SO good, and you can make it in 25 minutes or less.
A Cheesy Steak Sandwich So Good, You’ll Melt
- Textures and flavors. This sandwich really has it all, but we especially love the onions and melty cheese. It makes the best steak sandwich!
- Homemade spicy mayo. I’ve seen a lot of steak sandwich recipes with plain mayo or aioli, but I wanted mine with a kick. So, I mixed my mayo with sriracha, paprika, and lemon juice, and voila!
- Quick. Skirt steak sears quickly, so you can have this juicy steak sandwich ready to eat in under 30 minutes. It’s perfect for a light dinner or lunch.
Sandwich Ingredients
- Onions – You’ll thinly slice them and caramelize the onions with butter, sugar, salt, and pepper. White or yellow onions work best here.
- Baguette – I like to use small, seeded baguettes or ciabatta rolls. You can use any sturdy bread you’d like.
- Steak – I use skirt steak, but you can use flank steak, sirloin, or ribeye steak. Stick to quick-cooking cuts for the best results.
- Olive Oil – For searing. Cooking oil, like vegetable or avocado oil, also works.
- Gruyère Cheese – This is a mild Swiss cheese with a nutty flavor. Slice the cheese thin or grate it since you’ll be melting it for the sandwich. Other good options include Swiss cheese, Provolone, Havarti, and cheddar.
- Mixed Greens – Any greens you’d like. Try arugula, mesclun, etc.
Homemade Spicy Mayo
- Mayonnaise – You could make this sauce with only Greek yogurt for a lighter option, but I like the richness of mayo.
- Greek Yogurt – Or plain yogurt. You could also substitute sour cream or extra mayo.
- Sriracha – Or your choice of hot sauce or chili sauce. Sweet chili sauce will make a milder dressing.
- Paprika – Sweet or smoked.
- Lemon Juice – Freshly squeezed.
Recipe Tips
- Cut against the grain. This means cutting across the fibers/lines running through a piece of steak, not along them. Cutting against the grain keeps the meat tender and juicy.
- Don’t overcook the steak. Skirt steak cooks quickly, so a short 3 to 4 minute sear is all you need for a perfect medium-rare. Overcooking makes the steak tough.
- Toast both sides. Toast the top and bottom halves of bread to get the whole sandwich nice and crispy.
- Add the mayo afterward. Don’t add the mayonnaise to the bread before toasting, or it’ll melt right off!
- Don’t skip the sugar. Adding sugar to the caramelized onions not only sweetens them a little, but it also helps them caramelize faster.
- Make a wrap instead. Fold the ingredients into a burrito-sized tortilla wrap, egg white wrap, or cottage cheese flatbread.
What Else Can I Add to a Steak Sandwich?
In addition to the spiced mayonnaise in this recipe, here are some tasty ways you can customize this sandwich with add-ons. I’m partial to adding a little Macedonian red pepper relish, myself. 🙃
Serve With Au Jus
A fun way to serve these steak sandwiches is like a French dip sandwich, with au jus. Au jus is a light, savory gravy often made from pan drippings (see how to make it in my prime rib recipe). However, you can buy au jus seasoning mixes from brands like McCormick and Knorr. Pour the gravy into small bowls and dunk the sandwiches!
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For the Spiced Mayonnaise
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Caramelize the onions. Melt the butter in a skillet over medium-high heat. Add the thinly sliced onions to the skillet and cook, stirring, until they start to sweat. Then add sugar, salt, and pepper. Cook, stirring until the liquid has evaporated.
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Deglaze. Add 2 tablespoons of water to the onions and cook, scraping any browned bits from the bottom of the skillet. Repeat this process until the onions have that deep amber color. This process may take up to 30 minutes. Once done, set the onions aside.
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Spice up the mayo. Add the mayonnaise, yogurt, sriracha, smoked paprika, and lemon juice to a bowl. Stir to combine and set aside.
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Prepare the steak. Pat the steak dry, then season it to taste with salt and pepper. Heat the olive oil in a cast iron skillet over medium-high heat. Add the steak and sear it for 3-4 minutes per side, or until done to your preference, but don’t overcook it. Remove the steak from the skillet and set it aside to rest for 5 minutes before slicing. Meanwhile, prepare your bread.
To Assemble
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Prep. Preheat the oven to 450ºF. Cut the baguette in half by length to open it.
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Top with cheese and onions. Place the baguettes, cut side up, onto the baking sheet. Top the bottom part of the baguette with the caramelized onions and Gruyère cheese. Bake until the cheese melts.
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Add steak. Slice the steak thinly and place the slices over the melted cheese, then add the spiced mayonnaise and mixed greens.
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Finish and serve. Close the sandwich with the top part of the baguette, then cut it in half or into fourths. Serve.
- I do not recommend that you cook the skirt steak for too long. This 3–4-minute sear is perfect. The meat will stay pink through the middle.
- Toast the top half of the baguette with the bottom part because you want it all to be crispy.
- Do not spread mayonnaise while toasting the bread. It will just melt away.
- You can use baby arugula instead of mixed greens. Adding sun-dried tomatoes to the sandwich would be a nice addition.
- We add sugar to the onions to balance flavor but also speed up the caramelization process.
Serving: 0.25sandwich | Calories: 547kcal | Carbohydrates: 11g | Protein: 30g | Fat: 43g | Saturated Fat: 13g | Polyunsaturated Fat: 14g | Monounsaturated Fat: 14g | Trans Fat: 0.5g | Cholesterol: 104mg | Sodium: 641mg | Potassium: 365mg | Fiber: 1g | Sugar: 2g | Vitamin A: 750IU | Vitamin C: 8mg | Calcium: 312mg | Iron: 2mg
Nutritional info is an estimate and provided as courtesy. Values may vary according to the ingredients and tools used. Please use your preferred nutritional calculator for more detailed info.
How to Make the Best Steak Sandwich
The longest step is caramelizing the onions, but to achieve true greatness, it’s worth it! Follow the steps below to prepare the ultimate steak sandwich. This recipe makes two, but you can always double or triple it for friends.
- Caramelize the onions. Add the thinly sliced onions to a skillet with melted butter. Stir as the onions start to sweat. Next, sprinkle in the sugar and season the onions with salt and pepper. Keep cooking until the liquid evaporates.
- Delgaze. Now, deglaze the pan with 1-2 spoonfuls of water, scraping the bottom. Repeat, adding more water as the onions deepen in color. The process for caramelizing onions is low and slow. Don’t rush it!
- Make the spicy mayo. Set the caramelized onions aside. Meanwhile, combine the sauce ingredients and stir to combine.
- Cook the steak. Next, pat the steak dry and season it with salt and pepper. Sear the steak in a hot skillet with olive oil, about 3-4 minutes per side, until browned. Afterward, let the steak rest out of the pan for a few minutes.
- Melt the cheese. To prepare the bread, slice the baguettes in half and arrange them on a baking sheet, cut side-up. To each bottom half, add onions and sliced cheese. Place the buns into a 450ºF oven until the cheese melts (keep a close eye, it can happen quickly!).
- Assemble. Slice the rested steak into thin strips, against the grain. Place the steak on top of the melted cheese, followed by the prepared mayonnaise, and finally a layer of greens. Close the sandwich, slice it in half for easier eating, and dig in!
How to Store and Reheat Leftovers
- Store the steak separately. When possible, store the steak sandwich components before assembling. Keep the steak and leftover mayo in airtight containers in the fridge. Enjoy leftovers within 3-4 days.
- Reheat. Warm up the steak on the stovetop or in the microwave, taking care that it doesn’t overcook. Assemble the sandwiches as usual.
- Freeze. You can freeze the cooked steak for up to 2 months. Thaw it in the fridge before serving.
