To make the pickled onions, combine vinegar, sugar, and salt in a bowl. Add sliced red onion and let sit for at least 15 minutes while preparing the burgers.

Preheat a grill or skillet over medium-high heat. Cook Vegan Vaquero patties for 4–5 minutes per side, or until cooked to desired doneness. They should be browned and heated through.

Lightly toast burger buns.

In a small bowl, mix vegan mayonnaise, Dijon, and lime juice. Spread onto buns.

Assemble burgers with lettuce, avocado, tomato, jalapeño slices, and pickled red onion.

Serve immediately. Enjoy!