Combine flour, sugar, mustard powder and turmeric in small bowl. Stir in water. Let stand for 2 hours.
Combine mustard mixture, honey and vinegar in top of double boiler. Cook, whisking often, over boiling water until mixture just begins to thicken, about 3 minutes. Cook 2 minutes longer, whisking constantly, until slightly thickened. Stir grated orange rind into just-cooked mustard mixture (Mixture will thicken completely on standing.) turn into clean storage jar. Cover and refrigerate at least overnight or for up to 1 month.