For the cake:
- 1 1/2 cups granulated sugar
- 4 teaspoons packed orange zest (from about 2 medium oranges)
- 1 cup cake flour
- 12 large egg whites (1 1/2 cups), at room temperature
- 1 teaspoon cream of tartar
- 1 tablespoon freshly squeezed orange juice
- 1/4 teaspoon fine salt
- 3 pints strawberries (about 2 pounds), hulled and thinly sliced
- 1/4 cup freshly squeezed orange juice
For the cake:
Heat the oven to 325°F and arrange a rack in the middle. Mix 1 cup of the sugar with the orange zest in a small bowl until evenly combined; set aside.
Sift the cake flour through a fine mesh strainer 3 times onto a piece of parchment paper or into a large bowl. Then sift again with the remaining 1/2 cup sugar; set aside.
Place the egg whites in the bowl of a stand mixer fitted with a whisk attachment. (Be sure the bowl and whisk have been thoroughly cleaned.) Beat on high until just frothy, about 1 minute. Add the cream of tartar, orange juice, and salt and beat until the whites just begin to form soft, droopy peaks, about 2 minutes. Add the sugar-zest mixture 2 tablespoons at a time, letting it mix in before adding more, then beat until the whites are glossy and the peaks are droopy but hold onto a spatula, about 2 to 3 minutes more.
Remove the bowl from the mixer and sift a quarter of the cake flour mixture over the whites. Gently fold the dry ingredients into the whites with a rubber spatula. Continue to sift and fold in the remaining cake flour mixture, a quarter at a time, until all of it has been added.
Spoon the batter into a clean, dry 10-inch tube pan with a removable bottom. Tap the pan twice on the counter to burst any large air bubbles in the batter. Transfer to the oven and bake until the cake is springy to the touch and a wooden skewer inserted into the center comes out clean, about 35 to 40 minutes.
Invert the pan over the neck of a bottle (the cake should be hanging upside down—this keeps it from collapsing/deflating) until completely cooled, about 1 1/2 hours.
For the berries:
In a large bowl, combine the strawberries, orange juice, and sugar. Place in the refrigerator and let sit, stirring occasionally, until the sugar has dissolved and the strawberries have let off some juice, at least 15 minutes or up to 1 hour.
To remove and serve the cake:
Cut around the perimeter of the pan with a knife, remove the base, and cut around the tube and the base to release the cake completely. Slice with a serrated knife and serve with the soaked strawberries and their juices.