Pasta Salad with Prosciutto and Vegetables

Cook pasta according to package instructions in plenty of salted water until al dente. Rinse asparagus, trim ends. Cut off  heads and set aside, halve the rest lengthwise and cut into 2-3 cm (approximately 1 inch)  long pieces. Cook in boiling salted water until al dente, about 5 minutes. Peel onion, halve and cut into fine strips. Blanch if wanted and drain. Rinse tomatoes, pat dry and cut into slices. Drain pasta, rinse with cold water, drain again and cool. Cut prosciutto into small pieces. Combine with pasta, asparagus, onions and tomatoes.

Combine all ingredients for dressing. Season with salt and pepper.