To sugar the glass rims, pour the juice of 1 lemon into a shallow bowl and put the sugar on a small plate. Dip the rims of 2 glasses first in the lemon juice and then in the sugar. Set them aside to dry.
In a small bowl, combine the dried cherries with 2 ounces of cognac and microwave on high for 60 seconds. Set aside.
Combine the 3 ounces lemon juice with the remaining 4 ounces cognac, the Grand Marnier and 1 teaspoon of the marinated-cherry liquid. Fill a cocktail shaker three-quarters full with ice and pour in the cocktail mixture. Shake the mixer for a full 30 seconds (it's longer than you think!) and strain into the prepared glasses, either straight up or over ice. Thread 3 or 4 marinated cherries on small skewers and serve each drink ice cold with a skewer of cherries.