For the cake: Preheat the oven to 350 degrees F. Grease a 9-inch angel food cake pan with canola oil spray.
In the bowl of a stand mixer fitted with a paddle attachment, cream the butter and sugar on medium speed for 2 to 3 minutes. In a small bowl, mix the flour, baking powder and salt together. Add the flour mixture and the milk to the creamed butter and beat on low speed until thoroughly incorporated. Gently fold in the cranberries and pour the batter into the greased cake pan. Bake for 45 to 50 minutes, or until a toothpick inserted into the center comes out clean. Remove the cake from the oven, invert it onto a cooling rack, and let cool completely.
For the butter sauce: In a small saucepan over medium-low heat, melt the butter, then add the sugar and flour, stirring until smooth. Add the cream and vinegar and cook, stirring constantly, for 4 to 5 minutes, or until slightly thickened and bubbling. Add the vanilla and the food coloring. Cover and keep warm.
Cut the cake into slices and serve topped with warm butter sauce.