1. Peel and cook onions in boiling salted water for 15 minutes.
2. Drain well. Cut into two crosswise.
3. Arrange on buttered baking dish, cut sides up.
4. Chop garlic fine. Blend garlic with butter, parsley, salt and pepper. Gradually beat in lime juice.
5. Spread mixture evenly over the six half onions.
6. Cover and bake in moderate oven at 175° C (350° F) or Gas 4 for about 45 minutes basting from time to time.
7. Sprinkle with the breadcrumbs, return to oven and bake for another 10 to 15 minutes.