Why does your cherry pie filling turn black in your metal pan?

Cherry pie filling can turn black in a metal pan due to a chemical reaction between the acidity of the cherries and the metal, particularly aluminum or iron. This reaction can cause the pigments in the cherries to oxidize and darken, resulting in a blackened appearance. To prevent this, consider using glass or ceramic bakeware, which is non-reactive and won't interact with the filling. Additionally, adding a bit of lemon juice can help maintain the color by balancing the acidity.