1 grapefruit, cut into supremes over a bowl (see discussion above)
1 ripe avocado, cubed or sliced
1/4 red onion, sliced paper thin
1/4 c. best quality extra virgin olive oil
1/2 t. kosher salt
1 t. prepared dijon mustard (like Grey Poupon)
black salt and black pepper for finishing
Squeeze the leftover bits of grapefruit and the juice gathered while cutting the supremes, and measure 1/4 c. of it. Drink the rest, cook’s treat.
Mix the 1/4 c. of juice with the olive oil, kosher salt, and mustard in a jar and shake intensively to emulsify. Taste and add a little good vinegar if it needs more acidity. Leave it underseasoned so you can finish with the black salt.
Arrange the grapefruit, avocado, and onions on a plate, either individually or on a platter. Just before serving, drizzle on the salad and sprinkle with the black salt and black pepper.

This is off the web site http://herbivoracious.com/2008/01/recipe-grapefru.html.