To make this recipe gluten free, replace the all-purpose flour with a high-quality 1:1 gluten-free baking flour blend that contains xanthan gum, or add xanthan gum if your blend does not include it. Also confirm that the baking powder, vanilla extract, toffee chips, sweetened condensed milk, and any packaged ingredients are certified gluten free or free from cross-contact concerns, as some brands may include additives. Because gluten-free bundt cakes can be slightly more delicate, grease the pan very thoroughly and allow the cake to cool completely before removing it to help prevent breaking.