how do i sweeten dried tart cherries?

You could soak them in an orange or almond liqueur, and then add orange zest or almonds to the biscotti.

Where did you find these cherries? I would love to find dried fruit without added sugar and oil.

You could simmer them with orange or tangerine juice- something like a 1/3c. juice to 4 oz. fruit works well. They will absorb all the juice and make a nice pop of flavor and moisture in a cookie; I often do this with dried cranberries in chocolate chip cookies. The dried cherries are a bit large- you'd probably want to make largeish cookies.

I LOVE Maedl's idea of soaking them in Grand Marnier or Amaretto. I'm only mentioning brand names because they are truly superior and available in airplane sized bottles.

i live in northern MI and they sell them all over...u can try a specialty store on line that's called Cherry Republic out of Traverse City, MI