Preheat oven to 350°F (175°C). Do NOT grease your angel food cake pan; the batter needs to cling to the sides to rise.

In a medium bowl, whisk together 1/2 cup of the granulated sugar and the sifted cake flour. Set aside.

In a large, clean bowl of a stand mixer fitted with the whisk attachment, beat the egg whites on medium speed until foamy. Add the cream of tartar and salt.

Increase speed to medium-high and continue to beat until soft peaks form. Gradually add the remaining 1 cup of granulated sugar, 1 tablespoon at a time, beating well after each addition until stiff, glossy peaks form. The meringue should be very thick and hold its shape.

Gently fold in the vanilla extract and almond extract (if using).

Sprinkle about one-third of the flour-sugar mixture over the meringue. Gently fold it in with a rubber spatula until just combined. Repeat with the remaining flour mixture in two more additions, folding gently until no streaks of flour remain, being careful not to deflate the meringue.

While the cake batter is prepared, in a medium saucepan, combine 1 cup of the fresh raspberries, 1/2 cup granulated sugar, and 2 tablespoons of water. Bring to a simmer over medium heat, stirring occasionally, until the raspberries break down (about 5-7 minutes).

In a small bowl, whisk together the cornstarch and lemon juice until smooth. Stir this slurry into the simmering raspberry mixture. Cook, stirring constantly, until the sauce thickens, about 1-2 minutes.

Remove from heat and press the sauce through a fine-mesh sieve into a clean bowl to remove seeds. Let cool slightly.

Pour half of the angel food cake batter into the ungreased angel food cake pan.

Drizzle about half of the prepared raspberry sauce over the batter in the pan. Use a knife or skewer to gently swirl the raspberry sauce into the batter (do not overmix).

Carefully spoon the remaining cake batter over the raspberry layer.

Drizzle the remaining raspberry sauce on top and gently swirl again.

Bake for 35-45 minutes, or until the top is golden brown, springs back when lightly touched, and a wooden skewer inserted into the center comes out clean.

Immediately invert the cake pan onto its "feet" (if it has them) or over the neck of a bottle until completely cool (at least 1.5-2 hours). This prevents the cake from collapsing.

Once completely cool, run a thin knife around the edges of the pan and the inner core to release the cake. Carefully remove the cake from the pan.

Transfer to a serving plate. Garnish with additional fresh raspberries.

Dust with powdered sugar before serving, if desired.