HEAT oven to 350°F.
RESERVE 2 tsp. drink mix for glaze; set aside. Place remaining drink mix in large bowl. Add 1/2 cup water; stir until mix is dissolved. Add cake mix, sour cream, eggs, oil and half the lemon zest; beat with mixer until blended. Pour into well-greased and floured 12-cup fluted tube pan or 10-inch tube pan.
BAKE 42 to 45 min. or until toothpick inserted near center comes out clean. Cool cake in pan 10 min. Loosen cake from sides of pan with knife. Invert cake onto wire rack; gently remove pan. Cool cake completely.
PLACE cake on plate. Whisk together remaining 2 tsp. drink mix and 2 Tbsp. water in medium bowl. Gradually whisk in powdered sugar until blended; drizzle over cake. Sprinkle with remaining zest. Spoon blueberries into center and around bottom of cake.