Add strawberries, rhubarb, and sugar to a small sauce pan set over medium heat. Cook until rhubarb and strawberries begin to break down and soften, stirring often, about 5 minutes. In a small bowl whisk together cornstarch and water then add to berry mixture. Continue to cook until mixture is thickened and coats the back of a spoon.
Stir in vanilla, ginger, lemon juice, and salt and cook for an additional 1 to 2 minutes. If desired, smash berries and rhubarb or puree in a blender for a completely smooth texture. I like to leave some chunks of strawberries, but feel free to do what you need to do! Keep warm until ready to serve.
Meanwhile, use a pastry brush to coat both sides of angel food slices with butter. Place on grill over prepared coals. Do not cover. Grill for about 1 minute on each side, or until slightly charred all the way around.
To serve, place slices of angel food cake on a plate. Top with warm strawberry rhubarb compote and a scoop of ice cream. Enjoy!