Clean the vegetables, peel them if necessary and cut them into bite-sized pieces. Cook the asparagus, broccoli, celery and sugar snap peas in salted water until al dente (asparagus takes the longest at 5-8 minutes, the sugar snap peas are ready in 1-2 minutes), drain and rinse with ice water.
Now heat the butter in a pan, add the spring onions and tomatoes and sauté briefly. Add the balsamic vinegar and the remaining vegetables, toss briefly and season with salt and pepper.