Preheat oven at 375.
In a small brownie-sized pan (does not need to be greased) add in all the dry ingredients.
Mix all the wet ingredients in a separate bowl except the vinegar.
Add the wet ingredients to the dry ingredients and mix well until all dry ingredients are combined.
Add in the frozen raspberries and stir.
Pour in the 2 teaspoons of vinegar, stir, and immediately put the pan in the oven.
Bake for 25 30 minutes.
In the meantime, prepare the icing:
In a mixing bowl, add the margarine, powdered sugar, milk, and vanilla.
Mix (with a mixer) and add more powdered sugar or milk if needed to get the right consistency.
Once you have the right consistency, add in the food color and mix it all together.
When the cake has completely cooled off, spread on the icing.
Put the cake in the fridge for about an hour before serving.