This is best served warm out of the oven, and melty with the coconut cream on top. I've made this with both fresh and ground ginger, and I found that ground ginger tastes best. The cream can be made ahead of time. Store it in an airtight container in the refrigerator for up to 5 days.
Set the oven to broil, and line a baking dish with parchment paper.
Halve the grapefruits, and place them in the dish cut side up. Cut each grapefruit's flesh by tracing the perimeter and each segment with a knife. This will make it easier to scoop out and eat after it has been broiled.
Drizzle on the oil and 3 tablespoons maple syrup. Broil on high for about 10 minutes or until bubbly and slightly browned. Pull it out of the oven, cool for 5 minutes and sprinkle on the flake salt.
Prepare the coconut cream while the grapefruit is under the broiler.
In a small bowl whisk together the ginger, vanilla and remaining 1 tablespoon maple syrup and set aside. Then whip the coconut cream in a small bowl with a hand-mixer until it's blended. This will take only a few seconds. Then fold in the ginger mixture until well-combined.
Serve warm with a dollop of coconut cream and lemon zest.