This low carb 6 ingredient cast iron dinner using sirloin slices is one of those weeknight meals you can throw together in minutes and still feel proud serving to your family. Thick slices of sirloin get nestled into a hot cast iron skillet with just five other simple ingredients—bell peppers, onion, garlic, olive oil, and a splash of soy sauce or coconut aminos—for big flavor without a lot of fuss. It’s inspired by simple Midwestern skillet suppers, where everything comes together in one pan and makes the whole house smell amazing. The best part is watching everyone gather around the table and devour every last bite, with hardly any dishes left to wash.
Serve this skillet sirloin straight from the cast iron to the table for a cozy, family-style feel. For a low carb meal, pair it with a simple green salad, steamed or roasted broccoli, sautéed green beans, or cauliflower rice to soak up the savory juices. If you have mixed eaters at home, you can set out warm dinner rolls, cooked white or brown rice, or buttered egg noodles on the side for anyone who wants a heartier plate. A sprinkle of fresh parsley or green onions on top adds a nice pop of color and freshness.
Low Carb 6 Ingredient Cast Iron Sirloin SkilletServings: 4
Ingredients
1 1/2 pounds sirloin steak, cut into thick 1/2-inch slices
2 tablespoons olive oil, divided
1 large yellow onion, sliced into thin wedges
2 medium bell peppers (any color), sliced into strips
3 cloves garlic, minced
3 tablespoons soy sauce or coconut aminos (for gluten-free/low carb)
1 teaspoon kosher salt, or to taste
1/2 teaspoon black pepper, or to taste
Directions
Place your cast iron skillet on the stove over medium-high heat and let it heat up for 3 to 5 minutes until very hot. While it heats, pat the sirloin dry with paper towels and cut it into thick 1/2-inch slices. Season the slices on both sides with the salt and black pepper.
Add 1 tablespoon of olive oil to the hot skillet and swirl to coat. Arrange the raw sirloin slices in a single layer in the cast iron skillet, as close together as needed but without overlapping too much, creating that pretty process shot of beef slices snugly filling the pan. Let them sear, undisturbed, for 2 to 3 minutes until browned on the first side.
Flip the sirloin slices and sear the other side for another 2 to 3 minutes, just until nicely browned on the outside. The centers can still be a bit pink at this stage; they will finish cooking later. Transfer the browned sirloin slices to a plate and tent loosely with foil to keep warm, leaving any juices in the skillet.
Reduce the heat to medium. Add the remaining 1 tablespoon of olive oil to the same skillet. Add the sliced onion and bell peppers, stirring to coat them in the oil and beef drippings. Cook, stirring occasionally, for 5 to 7 minutes, until the vegetables are softened and starting to get some color around the edges.
Stir in the minced garlic and cook for 30 seconds to 1 minute, just until fragrant, being careful not to let it burn. Pour in the soy sauce or coconut aminos and use a wooden spoon to scrape up any browned bits from the bottom of the skillet—this adds lots of flavor and creates a simple, savory sauce.
Nestle the seared sirloin slices back into the skillet on top of and between the vegetables, along with any juices that collected on the plate. Spread them out so they are mostly in a single layer. Cook for another 2 to 4 minutes, turning the slices once, until the beef is cooked to your liking and everything is hot and coated in the sauce.
Taste and adjust seasoning with a little more salt or pepper if needed. Remove from heat and bring the cast iron skillet straight to the table (on a trivet or thick towel) so everyone can help themselves. Serve hot, spooning the peppers, onions, and pan juices over the sirloin slices.
Variations & Tips
For picky eaters, you can slice the sirloin into thinner strips instead of thick slices and cook them a bit longer so there’s no pink left—many kids feel better about fully cooked meat. If someone in your family isn’t a fan of peppers, swap them for sliced mushrooms or zucchini, or use half peppers and half another veggie to ease them in. To keep it strictly low carb and gluten-free, use coconut aminos or a certified gluten-free soy sauce and double-check any condiments you add. For extra flavor without adding more ingredients, finish the skillet with a small pat of butter off the heat and let it melt into the juices. You can also sprinkle on red pepper flakes for heat, or a handful of shredded cheese right at the end for a cheesier, more kid-friendly version. If you prefer a more steakhouse-style feel, serve the sirloin slices over a bed of sautéed spinach or cauliflower mash. Food safety tips: Always start by patting the beef dry with clean paper towels and washing your hands before and after handling raw meat. Use a separate cutting board and knife for the sirloin, and wash them well with hot, soapy water before reusing. Make sure the skillet is very hot before adding the meat to get a good sear without overcooking the inside. If you or someone in your home is pregnant, immunocompromised, or has specific health concerns, cook the beef to at least 145°F (63°C) and let it rest briefly. Refrigerate leftovers within 2 hours in a shallow container, and reheat thoroughly in a skillet or microwave before serving again.
