Mix the syrup: Place the orange juice, vanilla extract, honey and cornstarch in a saucepan. Whisk well until smooth and there are no more dry lumps of cornstarch.
Cook the syrup: Whisking constantly, bring to a boil and simmer for 1-2 minutes or until thickened to a medium syrup consistency.
Cool the syrup: Take the syrup off the heat. For a shorter cooling time, pour it into a bowl. Cool to room temperature. Whisk from time to time to avoid a skin on top.
Finish the dressing: Whisk the Greek yogurt into the cooled syrup. Chill in the fridge until ready to use.
Notes
I suggest not using this on fresh kiwi, pineapple or papaya (canned is fine!). The enzymes in the fresh fruit will break up the yogurt and turn it bitter and metallic.