1. Preheat your oven to 350°F (175°C) and prepare mini Bundt pans by lightly brushing them with oil.
2. In a bowl, sift together the cake flour, 3/4 cup sugar, and salt; set aside.
3. In a large mixing bowl, beat egg whites on medium speed until frothy. Add cream of tartar and vanilla extract. Increase speed to high, and gradually add the remaining sugar, beating until stiff peaks form.
4. Gently fold the flour mixture into the egg whites 1/4 cup at a time, being careful not to deflate the batter.
5. Divide the batter evenly into prepared mini Bundt pans. Swirl in red and blue food coloring using a toothpick for a marbled effect.
6. Bake for 20 to 25 minutes, or until the cakes are golden and a toothpick comes out clean.
7. Allow to cool in the pans for 10 minutes, then carefully invert onto a wire rack to cool completely.
8. Once cooled, top with fresh fruits like strawberries and blueberries for a patriotic touch.
9. Serve chilled or at room temperature.