Cake glaze
A powdered mix of starch and gelling agent, boiled with juice or water, that sets into a clear, sliceable layer over fruit on tarts and cakes.
Cake glaze in this sense is a powder of starch and a gelling agent such as carrageenan or locust bean gum, boiled briefly with liquid and usually sugar and poured while still hot over fruit arranged on a cake. As it cools it sets into a glossy layer, clear or tinted red depending on the type, that holds the fruit in place, keeps it from drying out and lets the cake be sliced cleanly. It tastes of very little itself; the flavour comes from the liquid, which is why the fruit's own juice is often used. In German-speaking countries it is on the baking shelf of every supermarket, while in the English-speaking world it is easier to find in Eastern European or German shops and online.
Substitute:
About a heaped tablespoon of cornstarch, or better arrowroot, boiled with a cup of juice and sugar gives a similar glaze, though it stays somewhat cloudier and softer and slices less cleanly. Heated and strained apricot jam adds shine and protects the fruit but does not form a firm layer and brings its own flavour. Gelatine sets more firmly but needs chilling and softens again in warmth.