Seared Sirloin and Roasted Potato Box with Herb Chimichurri
Sirloin seared and rested, then sliced against the grain over roasted red potatoes and cherry tomatoes, with a sharp parsley and oregano chimichurri spooned over the top.
Why You'll Love This Recipe
Opening the refrigerator on Tuesday and finding something worth taking to work starts with a Sunday afternoon. Four containers, twenty minutes of actual attention, and it is meant to be eaten cold or at room temperature, which is a rare and useful quality in a steak dish. Nothing about it needs a microwave or a plate. I started making it after too many weeks of sad desk salads, and it has held its place ever since because the sauce keeps doing its job on day three, when most lunches have given up entirely.
Chimichurri is where the flavor lives, and it is worth understanding what it actually is: a loose, coarse sauce of chopped herbs, vinegar, and oil that is supposed to be sharp enough to make you sit up. Chop the parsley by hand rather than in a food processor, which bruises it into a green paste, and make the sauce at least twenty minutes before you need it so the dried oregano can rehydrate in the oil. The steak wants a hard, fast sear in a dry cast-iron pan that has just started to smoke, four minutes a side, then ten full minutes of resting before a knife goes near it.
The slicing is the part that separates a good box from a chewy one. Sirloin has long, obvious muscle fibers, and cutting straight across them at a slight angle shortens every fiber on the plate. Cut the wrong way and the same steak fights you all the way through lunch. Spoon the sauce over while the potatoes are still warm so they drink some of it up, then let everything cool before the lids go on. Sirloin is dense enough that a container of this holds you through the afternoon, and the potatoes underneath keep it from being only meat and herbs.
Ingredients
- 1 1/2 lb sirloin steak, about 1 1/4 inches thick
- 1 1/2 lb small red potatoes, halved
- 6 tbsp olive oil, divided
- 1 cup finely chopped fresh parsley (about 1 large bunch)
- 1/2 cup finely chopped cilantro
- 2 tsp dried oregano
- 1 jalapeño, seeded and minced
- 3 tbsp apple cider vinegar
- 1 tbsp fresh lemon juice
- 1 1/2 cups cherry tomatoes, halved
- 1 1/2 tsp fine sea salt, divided
- 1 tsp black pepper, divided
Instructions
- Roast the potatoes: Heat the oven to 425°F (220°C). Toss the halved potatoes with 2 tablespoons of the oil and 1/2 teaspoon of the salt, spread them cut side down on a sheet pan, and roast for 30 to 35 minutes without stirring, until the flat faces are deep gold and the skins have gone papery.
- Make the chimichurri: Stir the parsley, cilantro, oregano, jalapeño, vinegar, lemon juice, 1/2 teaspoon of the salt, and 1/2 teaspoon of the pepper together in a bowl, then pour in 4 tablespoons of the oil and stir again. Let it sit for at least 20 minutes so the dried oregano softens and the sauce comes together.
- Sear the steak: Pat the sirloin very dry and season it with the remaining salt and pepper. Heat a dry cast-iron skillet over high until it just begins to smoke, lay the steak in, and cook 4 minutes a side without moving it, until the center reads 130°F (54°C) for medium-rare.
- Rest it properly: Move the steak to a board and leave it completely alone for 10 minutes. Cutting early sends the juices onto the board rather than keeping them in the meat, and sirloin is close-grained enough that it dries out quickly once those juices are gone.
- Slice against the grain: Find the direction the muscle fibers run and cut straight across them at a slight angle, about 1/4 inch thick. This shortens the fibers in every slice and is the single biggest thing separating tender steak from chewy steak.
- Build the boxes: Divide the potatoes and the raw cherry tomatoes among four containers or plates, lay the sliced steak over them, and spoon the chimichurri over everything while the potatoes are still warm. Cool them uncovered before the lids go on.
Variations
- Smoky: A teaspoon of smoked paprika stirred into the sauce takes it somewhere darker and echoes the crust on the steak.
- Green heat: Leave the jalapeño seeds in, or use two peppers, when you want the sauce to bite properly.
- Roasted tomatoes: Add the cherry tomatoes to the sheet pan for the last 10 minutes so they burst and go jammy against the potatoes.
- Other roots: Swap half the potatoes for parsnip or rutabaga cut to the same size for a sweeter, earthier base.
- Grilled: Cook the steak over hot coals for 3 minutes a side and let the smoke stand in for the cast-iron crust.
Storage & Leftovers
Assembled boxes keep for 3 days in the refrigerator and are meant to be eaten cold or at room temperature, which is how this dish is best anyway. Keep half the chimichurri back in a jar and spoon it on fresh, since the sauce already on the steak dulls a little overnight.
If you want it warm, reheat the potatoes and steak in a 350°F (175°C) oven for 8 minutes rather than in a microwave, which turns sliced sirloin gray and squeaky. Lift the tomatoes out first and add them back afterward, since they collapse within a minute or two of heat.
Chimichurri keeps for a week in a jar with a film of oil over the top, and it improves for the first two days as the oregano rehydrates. It does not freeze, since parsley goes black and slippery on thawing, but the roasted potatoes freeze perfectly well on their own.
Notes & Tips
- Cut side down, then leave them: Potatoes brown only where they touch metal. Every stir resets that, so set them face down once and do not move them.
- Make the sauce first: Chimichurri needs 20 minutes for the dried oregano to soften. Made at the last second, it tastes dusty.
- Dry the steak like you mean it: Surface moisture has to boil off before browning can start. A properly dried steak saves you a full minute of crust time.
- Get the pan properly hot: Cast iron should shimmer and just begin to smoke. A medium pan grays the outside of a sirloin before any crust forms.
- Rest, then slice, never the other way: Ten minutes of resting keeps the juice in the meat and off the board, and it is exactly enough time to halve the tomatoes.
- Sauce the potatoes warm: Chimichurri sinks into hot potatoes and sits on top of cold ones. Spoon it over as soon as the pan comes out of the oven.
Nutrition & Mindful Eating
- Steak, potatoes, and a green sauce are an old combination for good reason. The sirloin brings the protein, the potatoes bring the carbohydrate that makes this a real lunch, and the vinegar and herbs cut through both so the box still tastes bright at the last bite.
- Sirloin is a firm, close-grained cut that stays tender when it is cooked fast and sliced thin, and red meat is where the iron and B12 in this box come from.
- Parsley is the body of the chimichurri rather than a garnish, a whole bunch of it chopped by hand, and eaten in that quantity it brings real vitamin K and vitamin C to the plate.
- Red potatoes roasted cut side down go creamy inside and crisp where they met the pan, and cooling them in the container turns some of their starch resistant, which is the kind of starch the bacteria in your gut feed on.
- Cider vinegar and lemon do the sharpening here, the jalapeño gives a low heat that builds rather than stings, and the dried oregano softening in the oil is what makes the sauce smell like a grill even when the steak came off the stove.
- As you eat, notice how much of each bite is sauce rather than meat, let the vinegar and the herbs register before the steak does, and give the box the same attention at a desk that you would give it at a table.
Frequently Asked Questions
Can I use a different cut of steak?
Flank, skirt, and flat iron all suit this sauce and all want the same hard, fast sear. Skirt cooks in about 2 minutes a side, so watch it closely, and every one of these cuts depends on being sliced against the grain to eat tender.
My steak came out tough. What went wrong?
Almost always the slicing. Sirloin has long, obvious fibers, and cutting with them rather than across them leaves you chewing. It can also be temperature. Past 145°F (63°C) this cut tightens up and stays that way no matter how long you rest it.
Can I build these boxes for the whole week?
Yes, and it is the reason the recipe exists. Roast the potatoes and sear the steak on a Sunday, then divide everything cold among four containers. Keep the chimichurri in a jar and spoon it over each box on the morning you take it with you.
Does this suit a low-FODMAP lunch?
It does. The chimichurri here is built on parsley, cilantro, oregano, jalapeño, and vinegar rather than onion or garlic, and red potatoes sit well. If you keep garlic-infused olive oil, use it in the sauce for something closer to the classic version.