Ingredients:

• 1 large white or yellow onion
• 1 tablespoon olive oil
• 1 tablespoon apple cider vinegar
• 1/2 cup vegan mayonnaise
• 2 tablespoons ketchup
• 1 tablespoon dill relish
• 1/2 teaspoon pickle juice
• 1/4 teaspoon garlic powder
• 1/4 teaspoon sweet paprika
• 1/8 teaspoon salt
• 1/8 teaspoon freshly ground black pepper
• 2 Impossible Burger Patties or other plant-based burger patties, thawed overnight in the refrigerator if frozen
• 2 tablespoons Dijon mustard, optional
• 1 tablespoon salted vegan butter or olive oil
• 4 slices rye bread
• 4 slices smoked provolone, Swiss, or cheddar vegan cheese
• 2 tablespoons vegan Thousand Island, divided
• 1/2 cup caramelized onions, divided
• Sliced pickles, optional