Amaretto is indeed an almond liqueur. It is Kirschwasser, often simply called Kirsch, that is made with cherries.
Reducing the alcohol is a good idea and best done, imo, before the baste is made. I do this with wine for fowl bastes and for use in sausages, and for whiskies and liqueurs used in bastes for beef, pork and duck. For high alcohol products the item can be warmed in a pan and the alcohol (carefully) ignited or, for this type of product or items of lower proofs, simply brought to a simmer then reduced, uncovered, for several minutes, till much of the alcohol cooks off.
Note that reduction will concentrate flavors (often a good thing). Removing much of the alcohol first, before you mix the baste, allows you to get a better sense of how the baste will taste at finish (so taste it!). Of course you need to factor in the further evaporation and cooking of the baste when it is used, but this is easier to do when starting with a mix in which the alcohol was removed first.