Spray a 2 - 3 1/2 quart slow cooker with cooking spray.
In a large bowl, mix flour, sugar, cocoa, baking powder and salt in a bowl.
Stir in milk, oil and vanilla until incorporated and smooth.
Fold the cherry fruit filling into the batter. Spread in the bottom of the slow cooker.
To make the fudge sauce: In a small bowl mix the brown sugar,cocoa, and hot water. Pour evenly over the batter in the slow cooker.
Cover and cook on high for 2-2 1/2 hours or until toothpick inserted in center comes out clean. Turn off slow cooker and let stand for 30 minutes.
Serve with a scoop of vanilla ice cream.