In the bowl of a stand mixer fitted with whisk attachment, beat together sugar and meringue powder on low. Gradually add water and vanilla, and continue to beat at low speed until runny. Increase speed to medium and beat until thickened, approximately 5 minutes. Add remaining 1 tablespoon water, 1 teaspoon at a time, until runny (a stream comes off whisk when pulled out). Keep covered with a moist towel until ready to use.
Recipe by TeaTime Magazine at https://teatimemagazine.com/rose-sugar-cookies/