Boil the vinegar, sugar and water together in a saucepan. Add the onion and let the mixture cool in the refrigerator. Warm up a grill pan. Cut out the ends of the asparagus. Sprinkle the vegetables with olive oil. Grill them for 2-3 minutes on each side and add some salt and pepper. Keep them warm. Cut slices of cheese and place them on the toast. Add the grilled vegetables and the pickled red onions. Garnish with fennel tops. Sprinkle with peanuts and serve.
Tip: can be served alone or with grilled meats, such as beef steaks or chicken.