Preheat the oven to 325°F. Have a non-stick loaf pan ready, but do not spray it or flour it.

In a small bowl, combine 1/4 cup sugar, flour, and cornstarch. Whisk to combine and aerate and set aside.

To a large bowl or stand mixer bowl, add the egg whites, vanilla, cream of tartar, and salt. Beat on medium speed until foamy, about 30 seconds.

Leave the mixer on and stream in the remaining 1/2 cup of sugar, one tablespoon at a time until completely incorporated.

Continue beating on high speed until soft, floppy peaks form, about 4 minutes.

Remove from the stand mixer if using and fold in one-third of the dry ingredients by hand, using a spatula. Fold gently so as not to deflate the air you whipped into the egg whites.

Fold in each third of the dry ingredients completely, in increments, taking care not to deflate the batter and that no lumps remain.

Pour the batter into your loaf pan and bake for 38-42 minutes. You can tell the cake is done by touching the top, or cracks along the top – so long as neither are sticky, you’re good.

Immediately invert the loaf pan onto two cans or anything that will allow for air circulation underneath. The cake must cool upside down to prevent deflation.

When the cake is cool, run a knife around the edges and let the cake gently fall onto a cutting board.

Use a serrated knife or electric knife to cut the cake horizontally into three layers.

Measure two strips of plastic wrap that are 3-4 times the size of the cake out onto a clean surface. Place the bottom layer of cake in the middle of the plastic wrap.

Spread 3 tablespoons of jam onto the cake, creating an even coating.

Place the second layer on top, and repeat, topping with the last layer. Make sure each layer is aligned.

Wrap tightly within the plastic wrap, and press to make sure the cake is sticking together, and then place it back into the loaf pan you baked it in.

Refrigerate for at least 4 hours to set the layers.

Slice and serve with fresh berries and whipped cream.