Prepare raspberry puree by mashing raspberries with powdered sugar; set aside.

Preheat oven to 350°F (175°C). Make sure tube pan is clean and ungreased.

Sift cake flour, 1/2 cup sugar, and salt together three times.

Beat egg whites until foamy, then add cream of tartar. Add remaining sugar gradually until stiff peaks form.

Fold in vanilla and almond extract gently.

Fold dry ingredients into egg whites in three additions.

Pour half the batter into pan, add raspberry puree in dollops, then repeat with remaining batter and puree. Swirl gently.

Bake 38–45 minutes until top is golden and cake springs back to touch.

Invert pan and cool upside down for 1 hour.

Run a knife around pan edge to release and serve with fresh raspberries or whipped cream.