Place prunes in a small saucepan and add enough water to cover.
Bring to a boil, lower heat, and cook until prunes are soft.
Drain and reserve liquid.
Pit prunes; puree in blender container or food processor and set aside.
Combine egg, 1 tablespoon reserved liquid, and vanilla.
Pour mixture into a preheated nonstick skillet or omelet pan.
Cook until bottom is brown.
Top with prune puree and fold omelet in half.
Serve at once on a heated serving plate.