Amounts are suggestions only. You can use lettuce or mixed greens instead of mache. Use pink or ruby grapefruit. As AmandaInOz suggested, I am revising this recipe to include a Dijon dressing. I like Trader Joe's Dijon mustard with white wine.
In the salad bowl, mix mustard well with oil; add juice and continue to blend until thoroughly blended.
For the salad:
Peel, section and de-membrane the grapefruit and place in salad bowl.
Add sliced avocado and a few handfuls of mache leaves or greens.
Salt to taste.
Sometimes I simply halve the grapefruit and scoop out the sections with a grapefruit spoon. This is messier and less attractive than carefully removing all the membranes of each grapefruit section, but it saves a little time.