Preheat a grill to high heat.
Lightly grease the cut sides of the grapefruit(s) and leek with nonstick cooking spray. Grill them both, cut-side down, until they are charred and the leeks are tender, about 2 minutes for the grapefruit and 3 minutes for the leeks. Let cool slightly.
Juice the grapefruit into a large mixing bowl (you should have about 1/2 cup juice). Chop the leeks and add them to the bowl with the grapefruit juice. Add the olive oil, honey and some salt and pepper to the bowl and whisk to combine. Reserve.
Lightly grease the cut sides of the romaine with nonstick cooking spray. Grill the lettuce, cut-side down, until aromatic and charred, about 30 seconds. Transfer the lettuce to serving plates. Drizzle it with the prepared dressing and garnish with almonds and shaved cheese. Serve immediately.
Serving Suggestion: Because my husband is one of those "this is good, but I'm still hungry" kind of people, I added some grilled chicken alongside. Do as you please - this would be perfect with a fillet of salmon, pork chop or all on its own.