Mystery Cake - cooking recipe

Ingredients

2 c. all-purpose flour
1/2 tsp. salt
1/2 tsp. cinnamon
1/4 tsp. nutmeg
1/4 tsp. cloves
1 Tbsp. baking powder
1 c. sugar
2 eggs
1/2 c. butter
1 (10 1/2 oz.) can condensed tomato soup (mystery ingredient)
1 c. chopped walnuts
1 c. chopped raisins

Preparation

What gives this cake its pretty color and rich flavor?