In a large pot of boiling salted water cook farfalle until al dente. Drain.
Meanwhile, in a large frypan saute onion in butter or margarine until soft and tender. Add prosciutto and saute with onion 2 minutes. Add dry white wine and let simmer for 2 additional minutes. Add tomatoes, peas and ground black pepper; stir well. Cover and simmer for 10 minutes.
In a large bowl toss drained farfalle pasta with prosciutto mixture. Serve warm.