Steak Sandwiches with Crispy Onions

Total Time

Prep: 45 min. + marinating Grill: 15 min.


6 servings

Updated: Oct. 27, 2023
I created this steak sandwich recipe for my husband. Fried onions are a family favorite, and I thought it would be amazing to put them on a sandwich. The chimichurri-inspired mayo gives fabulous freshness and flavor. —Renee Seaman, Green Township, New Jersey
Steak Sandwiches with Crispy Onions Recipe photo by Taste of Home


  • 1 large sweet onion
  • 3 cups buttermilk
  • 2 cups minced fresh cilantro
  • 1 cup minced fresh parsley
  • 2 garlic cloves, minced
  • 1/2 teaspoon plus 2 teaspoons salt, divided
  • 1/4 teaspoon pepper
  • 1/2 cup mayonnaise
  • 1/2 cup plus 3 tablespoons olive oil, divided
  • 1 beef flat iron steak or top sirloin steak (1-1/2 pounds)
  • 1-1/2 cups all-purpose flour
  • 3 tablespoons taco seasoning
  • Oil for deep-fat frying
  • 12 slices Italian bread (1/2 inch thick)
  • Optional: Fresh arugula and sliced tomato


  1. Cut onion into 1/4-in. slices; separate into rings. Place in a large bowl or shallow dish. Add buttermilk; turn to coat. Refrigerate at least 4 hours or overnight.
  2. In a small bowl, combine cilantro, parsley, garlic, 1/2 teaspoon salt, and pepper. Remove 2 tablespoons herb mixture; stir into mayonnaise. Refrigerate until serving. Stir 1/2 cup olive oil into remaining herb mixture. Reserve 2 tablespoons oil mixture for serving. Place remaining oil mixture in a large bowl or shallow dish. Add beef; turn to coat. Refrigerate at least 4 hours or overnight.
  3. Drain beef, discarding marinade. Grill beef, covered, over medium heat or broil 4 in. from heat until meat reaches desired doneness, 7-9 minutes on each side (for medium-rare, a thermometer should read 135°; medium, 140°; medium-well, 145°).
  4. Meanwhile, drain onion rings, discarding marinade. In a shallow dish, combine flour, taco seasoning and remaining 2 teaspoons salt. Roll onion rings in flour mixture. In an electric skillet or deep-fat fryer, heat 1 in. oil to 375°. Fry onion rings, a few at a time, until golden brown, 1 to 1-1/2 minutes on each side. Drain on paper towels; keep warm.
  5. Remove steak to a cutting board; brush with reserved 2 tablespoons oil mixture. Brush bread with remaining 3 tablespoons olive oil. Grill bread over medium heat until toasted, 30-60 seconds on each side.
  6. Spread mayonnaise mixture over 1 side of each toast. Thinly slice steak. Top 6 slices of toast with steak, fried onions and, if desired, arugula and tomato slices. Top with remaining toast.

Nutrition Facts

1 sandwich: 930 calories, 58g fat (10g saturated fat), 75mg cholesterol, 1719mg sodium, 68g carbohydrate (6g sugars, 4g fiber), 32g protein.