1. Peel and cut the onions into thin rings

2. Blanch the onions in boiling salted water for 1minute

3. Drain them thoroughly and put them on one side to cool

4. Slice the tomatoes and arrange them overlapping the cooled onion rings round a large shallow serving dish and leave the center clear

5. Season lightly with salt and pepper

 To make the dressing:

1. Halve and stone the avocados

2. Scoop out the flesh and put it into a liquidizer

3. Add the soured cream, French dressing, garlic and salt and pepper to taste

4. Puree the ingredients until smooth then adjust the seasoning

5. Shortly before serving, spoon the avocado dressing into the center of the salad

List of ingredients required:

(serves 12 people)

2 large Spanish onions
Salt
Freshly ground pepper
3 lb (1.4kg) Mediterranean tomatoes

For the dressing:

2 ripe avocados
2 cloves crushed garlic
1/ 4 pint (150ml) soured cream
1/ 4 pint (150ml) French dressing
Salt and freshly ground pepper