1. Peel and core pears. Cut fruit into 1/2-inch chunks.
2. Place pears in a 2- to 3-quart pan. Add lemon peel, lemon juice, cranberries, ginger, and 1/4 cup sugar. Mix, cover, and stir occasionally over medium heat until fruit is tender when pierced, 10 to 15 minutes.
3. Add vanilla, crème de cassis, and more sugar, if desired. Serve warm or cool. If making ahead, cover and chill up to 3 days.