Whisk together the grapefruit juice, honey, cointreau and lemon juice in a pot. Sprinkle with the gelatin powder and set aside for 15 minutes to bloom.
Heat the mixture over medium-low heat, whisking continuously for 4-5 minutes. Do not bring to a boil.
Pour the mixture through a fine mesh sieve into a 8×4 or 9×5 loaf pan (no need for parchment paper) and chill around 45 minutes, until firm.
Run a small offset spatula or knife around sides of pan to loosen the candy then gently peel away candy from bottom of the pan. Cut into small cubes or punch out into desired shapes with small cookie cutters. Once you cut the slices, they need to stay separate from each other or they will melt back together.