What size pan should I use if I want to split a recipe in half that calls for a 13x9 inch pan?
I have a couple of 8.5" x 6.5" pans (designed for toaster ovens) that I use for exactly this. The height is about the same as a standard 13" x 9" pan. I've split solid dishes like carrot cake or Spanish Bar Bread and looser ones like Spinach Marie or macaroni and cheese successfully. Just remember to check on the dish earlier than usual as the smaller portions will bake quicker.