Can I avoid overcooking my candied lemon decorations? I've been tweaking my grandmother's fruitcake recipe all month, and as part of this adventure I tried to make it a little fancier by adding some candied orange and lemon slices on top.

This looked really cute and decorative when I put the candied slices on the raw batter before going in the oven. But this has to bake for 2.5 hours at 275°F. After that amount of time, the candied citrus was significantly darker (not burnt black, but definitely brown) and crunchy rather than chewy. It's not quite as unpleasant as I expected, but over-caramelized lemon crunches is not what I wanted.

I had previously tried just dropping candied lemon slices on the baked fruitcake, but it is not a moist cake and they fall off (in transport, when slicing, etc.).

Is there a way to affix the candied citrus slices to my cake without putting them through an apparently brutal baking process?
Try gluing them to the cooked cake with a sugar syrup or caramel.  Caramel is quite sticky, so it should hold the candied citrus on the cake with no problems, at least during transport.  How hard your caramel is will probably affect how well it cuts, but I think a somewhat softer caramel (or a thicker sugar syrup) would probably cut just fine with a reasonably sharp knife.

Alternatively, you could always try standing them up vertically in the cake, depending on how stiff your slices are and whether that's a look you're interested in for the assembled cake.