Memphis Blues Burgers with Mustard Sauce

• 1 small red onion, cut into 1/4-inch slices
• 1 pound ground beef
• 1/2 small onion, grated
• 1/4 teaspoon salt
• 1/2 teaspoon freshly ground black pepper
• 8 small potato rolls, split in half
• 2 medium-sized ripe tomatoes, sliced
• Sliced pickles, for garnish
• Leaf lettuce, for garnish
• 1 recipe Mustard Sauce (see below)
• 3 tablespoons mayonnaise
• 1 tablespoon Dijon mustard
• 1 teaspoon apple-cider vinegar
• 1/4 teaspoon cayenne pepper
• Kosher salt
• Freshly ground black pepper

1. FOR THE BURGERS:
2. Preheat a flat-top grill pan to high.
3. Place the sliced onion on the grill, and cook until lightly charred and tender, about 10 minutes.
4. In a medium bowl, combine the ground beef, grated onion, salt, and pepper.
5. Make eight small burgers equal in size, about 3 inches across.
6. Cook the burgers on the flat-top for 3 to 4 minutes on each side.
7. Serve on the split rolls with grilled onions, tomatoes, pickles, and Mustard Sauce.
8. FOR THE MUSTARD SAUCE:
9. Stir all the ingredients together in a small mixing bowl.

red onion, ground beef, onion, salt, freshly ground black pepper, potato rolls, tomatoes, pickles, recipe mustard sauce, mayonnaise, mustard, applecider vinegar, cayenne pepper, kosher salt, freshly ground black pepper

Taken from www.cookstr.com/recipes/memphis-blues-burgers-with-mustard-sauce (may not work)