Step 1 In a medium, heavy-bottom saucepan, bring the water, sugar, rose hip tea and cardamom to a gentle simmer and cook slowly until the sugar is dissolved and the rose hips have softened, 12 to 15 minutes.
Step 2 Increase the heat to medium and bring the mixture just to a boil. Remove from heat and stir in the lemon juice and rose water. Set aside to cool while the doughnuts are made, then strain before using. If not using immediately, cover and refrigerate until needed.