Preheat oven to 350degreesF. Lightly coat an angel-food cake pan or fluted tube pan with cooking spray. Set aside.
In a large mixing bowl, combine cake mix, yogurt, and eggs. Beat with an electric mixer on low speed for 30 seconds. Scrape down sides of bowl; beat for 2 minutes on medium speed. Spoon batter into prepared pan. Bake in preheated oven for 30 to 35 minutes or until cake tester inserted in center comes out clean. Cool cake in pan for 15 minutes. Turn cake out onto a wire rack and cool completely.
In a small bowl, stir together frosting and the garam masala. Frost cake top with frosting. Sprinkle walnuts over frosting.