Can you use plain flour instead of cornflour in lemon meringue filling?

It is generally not recommended to substitute cornflour (cornstarch) with plain flour in lemon meringue filling. Cornflour is essential in achieving the desired consistency and texture of the filling, as it acts as a thickening agent. Plain flour, on the other hand, does not possess the same thickening properties as cornstarch and would likely result in a runny or loose filling. If you do not have cornstarch on hand, you may consider alternative thickeners such as arrowroot powder or tapioca flour, which are closer in functionality to cornstarch.