Wearing gloves, peel the salsify. Trim the ends and cut into 3 cm diagonal pieces. Place in vinegar water (combine apple cider vinegar with water) with a pinch of salt and a small amount of sugar. Cook on medium heat for 20 minutes until tender.
Dice the day-old pretzels into bite-sized pieces. Heat some vegetable fat in a pan over medium heat. Toast the bread cubes for 3-5 minutes, stirring occasionally, until golden and crispy.
Cut the red onions into rings. Add a small amount of vegetable fat to the pan. Toast the onion rings on medium heat for 3-4 minutes, sprinkling with a little sugar, until softened and lightly caramelized.
Wash the rocket and distribute evenly among four plates. Top with the toasted bread cubes. Drain the cooked salsify. Fry the salsify in the pan on medium heat for 2-3 minutes on all sides until browned. Arrange on the salad with the onion rings on top.
Drizzle the salad with vinegar and rapeseed oil. Sprinkle coarse mountain salt over it to taste. Serve immediately.