Boon of spell recall (p 232 of the Dungeon Master’s Guide) Says that you can cast any spell you know or have prepared without using a spell slot.
Can that spell be cast at a higher level than the minimum required to cast the spell?
For example could I cast magic missile as a 9th lv spell (assuming I normally had 9th lv spell slots)?
My reason for thinking that you can is that other boons (like spell mastery) specify that the spells are cast at their lowest level. While Boon of spell recall does not.