Preheat the oven according to the directions on the angel food cake mix box, usually 350°F (175°C). Make sure the tube pan is clean and completely dry. Do not grease the pan.
Place the raspberries in a small bowl. Sprinkle with flour and gently toss to coat. Set aside.
Prepare the angel food cake mix according to the package instructions. Beat until the batter is light, fluffy, and airy.
Gently fold the floured raspberries into the batter using a rubber spatula. Use slow and gentle strokes to avoid deflating the batter.
Spoon the batter evenly into the ungreased tube pan. Smooth the top lightly and tap the pan gently on the counter to remove large air bubbles.
Bake the cake according to the time listed on the box, usually until the top is lightly golden and springs back when touched.
Remove the pan from the oven and immediately turn it upside down. Let the cake cool completely in this position.
Once cooled, run a knife around the edges and center tube. Carefully remove the cake and slice using a serrated knife.