Step 1In a small bowl using a fork or spoon, smash the tangelo zest with the sugar to moisten the sugar with the fruit's aromatic oils. Transfer the mixture to a 1-quart heavy-bottom saucepan along with the cornstarch and a tiny pinch of salt. Whisk in just enough of the tangelo juice to make a smooth slurry, then add the remaining juice and whisk to smooth.
Step 2Place the pan over medium heat and gently bring the mixture to a boil. Cook, stirring frequently, until the juice has thickened, just a few minutes. Cook for 1 minute more, then remove from heat and whisk in the butter, orange flower water and honey. This makes a generous 2 cups of pudding.
Step 3Divide the pudding among juice glasses or Champagne glasses and refrigerate until set, about 2 hours.