Grilled Flank Steak, Onion, and Poblano Pepper Fajitas served on a sizzling platter, featuring tender slices of marinated flank steak, charred onions, and smoky poblano peppers, ready to be wrapped in warm tortillas for a flavorful fajita experience

Grilled Flank Steak, Onion, and Poblano Pepper Fajitas

5.0 from 1 vote
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These grilled flank steak fajitas use creamy Monterey Jack cheese sauce instead of shredded cheese that falls off the tortilla. The marinade tenderizes the steak with lime juice, cumin, and chili powder, while high-heat grilling creates char on the meat, poblano peppers, and onions. The result is smoky, rich fajitas with actual depth.

Why This Marinade Tenderizes Flank Steak

Flank steak needs acid to break down dense muscle fibers. This marinade combines lime juice with olive oil, cumin, chili powder, paprika, and oregano. Brown sugar balances acidity and helps with caramelization. Beef broth adds savory depth. Marinate for at least two hours, or overnight for best results.

Grilling Creates Better Flavor Than Skillet Cooking

Most fajita recipes use a skillet, which steams vegetables and prevents proper searing. Grilling over direct high heat chars the flank steak exterior while keeping the interior medium-rare. Poblano peppers and onions get actual char marks and smoky flavor. Get your grill screaming hot before cooking.

Making Cheese Sauce That Actually Sticks

Shredded cheese falls off tortillas and never melts properly into meat. This Monterey Jack sauce fixes that. Start with butter and garlic, add cream cheese and sour cream for thickness and tang, then melt in shredded Monterey Jack. Stir constantly over low heat until smooth and glossy. The sauce coats every piece of steak and vegetable instead of sliding off.

Grilling Poblanos and Onions Properly

Place whole poblano peppers on the hottest part of your grill. Let them char on all sides until the skin blackens and blisters. Steam in a covered bowl for ten minutes, then peel off the skin. Slice onions into thick rounds (at least half an inch) so they hold together. Brush with oil and grill until charred and sweet.

Slicing Flank Steak Against the Grain

After grilling to medium-rare (130-135°F internal temperature), rest the steak for ten minutes. Look at the muscle fibers and slice perpendicular to them in thin quarter-inch strips. Cutting against the grain makes each bite tender instead of chewy.

Building Better Fajitas

Warm flour tortillas on the grill for fifteen to twenty seconds per side until they develop light char marks. Layer with sliced steak, ladle cheese sauce generously over the meat, then add grilled poblanos and onions. Finish with fresh cilantro and lime juice for brightness that cuts through the richness.

Why This Recipe Works

The marinade and cheese sauce can be made ahead. Actual grilling takes under twenty minutes once the fire is hot. The combination of smoky steak, charred poblanos, sweet onions, and creamy cheese sauce creates layers of flavor that make these fajitas better than standard versions.Retry

Grilled Flank Steak, Onion, and Poblano Pepper Fajitas

Recipe by Kyle Taylor
5.0 from 1 vote
Course: MainsCuisine: Tex-MexDifficulty: Medium
Servings
+

4

servings
Prep time

4

hours 
Cooking time

30

minutes
Total time

4

hours 

30

minutes

Grilled Flank Steak, Onion, and Poblano Pepper Fajitas are a harmonious Tex-Mex delight that unite succulent grilled flank steak, smoky poblano peppers, and caramelized onions with a luscious Monterey Jack cheese sauce, all encased in warm flour tortillas.

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Ingredients

  • For the Marinade:
  • 2 pounds flank steak

  • 1/4 cup extra virgin olive oil

  • 1 cup beef broth

  • 4 cloves of garlic, minced

  • 1 tablespoon cumin

  • 1 tablespoon paprika

  • 1 tablespoon chili powder

  • 2 tablespoons brown sugar

  • 1/2 tablespoon dried oregano

  • 2 limes, juiced

  • For the Fajitas:
  • 3 large poblano peppers

  • 2 large onions, thickly sliced

  • 2 tablespoons extra virgin olive oil

  • 8 medium flour tortillas

  • for garnish, cilantro leaves

  • for serving, lime wedges

  • For the Monterey Jack Cheese Sauce:
  • 1 cup Monterey Jack cheese, shredded

  • 2 tablespoons unsalted butter

  • 2 cloves of garlic, minced

  • 1/4 cup sour cream

  • 1/4 cup cream cheese

  • to taste, salt and ground black pepper

Directions

  • Marinate the Flank Steak:
  • In a bowl, combine the extra virgin olive oil, minced garlic, ground cumin, chili powder, paprika, dried oregano, lime juice, beef broth, brown sugar, salt, and black pepper to create the marinade. Place the flank steak in a resealable plastic bag or a shallow dish. Pour the marinade over the steak, ensuring it is well-coated. Seal the bag or cover the dish and refrigerate for at least 4 hours, or preferably overnight, to marinate.
  • Grill the Flank Steak, Poblano Peppers, and Onion:
  • Preheat your grill to medium-high heat. Remove the flank steak from the marinade and let any excess drip off.

    Grill the steak for about 4-5 minutes per side for medium-rare or to your preferred level of doneness. Cooking times may vary based on the thickness of the steak. Remember that flank steak is best when served medium-rare to medium for tenderness.

    Coat the poblano peppers and onion with extra virgin olive oil. Place the whole poblano peppers and thickly sliced onion directly on the grill grates. Grill them until the poblanos are charred and blistered on all sides, and the onion slices are tender and slightly caramelized, about 8-10 minutes.

    After grilling, transfer the steak to a cutting board, and let it rest for 5-10 minutes before slicing it thinly against the grain. Place the poblano peppers in a covered bowl or a plastic bag for a few minutes to steam and make peeling easier. Then, remove the charred skin, seeds, and stems from the poblano peppers. Chop them before serving (optional).
  • Prepare the Monterey Jack Cheese Sauce:
  • In a small saucepan over medium-low heat, melt the butter. Add the minced garlic and sauté for about 1 minute until fragrant. Reduce the heat to low, add the cream cheese, and stir until it’s completely melted and smooth. Gradually whisk in the sour cream until the mixture is well combined and creamy. Stir in the shredded Monterey Jack cheese until it’s fully melted and the sauce is smooth. Season with salt and ground black pepper to taste. Keep the sauce warm over low heat, stirring occasionally.
  • Assemble the Fajitas:
  • Warm the flour tortillas on the grill or in the oven according to the package instructions.
    To assemble the fajitas, place a few slices of the grilled flank steak on each tortilla, followed by the Monterey Jack cheese sauce. Top with the grilled poblano peppers and onion.

    Serve the fajitas warm with garnishes such as lime wedges and fresh cilantro leaves.
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