The Secret to Easy Skillet Filet Mignon Steak Tacos

⏲ ~39 min total · prep 4 · cook 35 · 4 servings

By the KFI Test Kitchen · Tested & approved by Jason Lieu, KFI recipe editor

Published Sep 15, 2026 · Updated Sep 15, 2026

Ingredients

• 1 lb filet mignon (1-2 tenderloin steaks), cut into 1-inch cubes
• 1 tbsp avocado oil
• 1 1/2 tsp chili powder
• 1 1/2 tsp ground cumin
• 1/2 tsp smoked paprika
• 1 tsp kosher salt
• 2 tbsp butter
• 2 cloves garlic, minced
• 1 lime, halved
• 8 low-carb flour tortillas (4-6 g net carbs each)
• 1/2 cup crumbled cotija cheese
• 1/2 avocado, sliced, plus 1/4 small red onion, thinly sliced

Instructions

1. Toss the steak cubes with the chili powder, cumin, smoked paprika, and salt until every face is coated in the spice blend.
2. Heat a cast-iron skillet over high heat for 3 minutes, until a flick of water skitters and flashes off the surface, then add the avocado oil.
3. Lay the cubes in a single layer with breathing room and sear untouched for 90 seconds, until a dark brown crust forms on the underside; flip and sear 60 seconds more for medium-rare (130°F).
4. Drop the heat to medium-low, drop in the butter and garlic, and tilt the pan, spooning the foaming garlic butter over the cubes for 30 seconds — this baste is the secret.
5. Squeeze in half the lime, toss the cubes through the pan sauce for 15 seconds, and scrape everything onto a plate immediately; filet goes from rosy to gray fast.
6. Char the tortillas 20 seconds per side in the hot dry pan, then build: steak, cotija, avocado, red onion, and a squeeze of the remaining lime.

Why this recipe works

• Cast iron, dry heat, no moving Three minutes of preheating and 90 untouched seconds build the dark crust that makes 1-inch cubes worth eating. Cubes shifted early sear on one face and gray on the rest.
• The garlic butter baste Tilting the pan and spooning foaming butter and garlic over the seared cubes for 30 seconds finishes them like a steakhouse. It costs half a minute and zero carbs.
• Filet rewards restraint Tenderloin stays rosy and tender at 130°F, and a few degrees more turns it gray and dry fast. The recipe pulls the meat onto a plate immediately for that reason.

Tips for making this recipe well

Cube size matters

One-inch cubes give 90 seconds per side enough room to crust without overcooking the center. Smaller cubes are done before the pan finishes the sear.

Test the pan with water

A flick of water that skitters and flashes off the surface means the cast iron is ready. Oil added too early burns, and meat added too early welds.

Have everything else ready

The sear and baste take under 4 minutes total. Tortillas, cotija, avocado, and red onion should already be on the counter before the oil goes in.

Char the tortillas last

Twenty seconds per side in the still-hot dry pan warms them and spots them with char. Do it while the cubes rest off the heat so nothing cools waiting.

Pull the lime at the end

The recipe squeezes half the lime into the pan sauce and holds the rest for the table. Acid over seared filet flatlines the crust if it sits; squeeze at the moment of eating.

Serving suggestions

Build them at the counter and eat them immediately, because seared filet cubes cool faster than any other cut. Charred tortilla, five or six cubes, cotija, avocado, red onion, and the final squeeze of lime, in that order. The ingredient list calls for 8 low-carb tortillas at 4-6 g net carbs each, so the filling's 3.0 net carbs per serving is only part of the evening's math. Keep the remaining lime half on the board for whoever wants more acid on taco two.

Storage and meal prep

Store leftover seared cubes in a shallow container for 3 to 4 days, knowing reheated filet never returns to medium-rare. Warm them briefly in a pan over medium-low, only until the chill leaves, and accept some gray at the edges. The cubes freeze for 2 to 3 months, though tenderloin is a poor freezer candidate; thaw overnight and fold them into eggs where texture matters less. Keep tortillas and toppings stored separately.

Variations worth trying

• Sirloin instead Sirloin cubes cost less and take the same spice blend and sear times; expect slightly more chew.
• Lettuce wraps Skip the tortillas and wrap the cubes in butter lettuce; the filling alone runs 3.0 net carbs per serving.
• Extra heat Add a pinch of cayenne to the spice blend or char a jalapeño in the pan alongside the tortillas.
• Steak bowl Pile the cubes over shredded lettuce with the same toppings and skip the folding entirely.

Frequently asked questions

Can I use a different cut?

Yes. Sirloin or ribeye cubes work with the same timing, and ribeye brings more fat to the pan. Filet is the tender option, which is why a 20-minute dinner leans on it.

Why 130°F?

That is medium-rare for beef, and filet is at its best there. Beef steaks are safe cooked to that temperature, and holding it there keeps the tenderloin rosy instead of gray.

No cast iron?

Any heavy skillet preheated the same 3 minutes works. Thin pans drop temperature when the meat lands, and the crust suffers for it.

How do I keep the cubes from overcooking?

Single layer with space between cubes, one flip, and off the heat the moment the baste finishes. Filet carries heat forward after it leaves the pan.

Can I season the cubes ahead?

Yes. There is no liquid marinade here, only a dry spice rub, so the cubes hold seasoned in the fridge for a few hours; blot any surface moisture before they hit the pan.

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