Arc Burgers

Ingredients

• BURGERS
• 1 pound boned beef rib-eye steak
• 3/4 pound boned beef short ribs (or slice meat from 1 3/4 lbs. bone-in short ribs; 3 or 4 ribs)
• 1 large yellow onion, thinly sliced
• 2 tablespoons extra-virgin olive oil
• 4 ounces thick-cut smoked bacon
• 3 garlic cloves, minced
• 1 1/4 teaspoons kosher salt
• 1 teaspoon pepper
• 2 tablespoons chopped chives
• 2 tablespoons finely chopped chervil or parsley
• 1/4 cup duck fat* or cooled melted butter
• TO SERVE
• 1/2 cup mayonnaise
• 1 teaspoon lemon zest
• 1/4 teaspoon pepper
• 1 tablespoon Dijon mustard
• 2 tablespoons melted butter
• 2 large heirloom tomatoes, 1 red and 1 yellow, thickly sliced crosswise
• 1/4 teaspoon kosher salt
• 8 soft lettuce leaves, such as butter lettuce
• 1 teaspoon vinaigrette, homemade* or store-bought
• About 4 oz. crumbled Roquefort or coarsely shredded extra-sharp white cheddar cheese (optional)
• 1/2 red onion, sliced into very thin rings