Preheat your oven to 325°F. Do not grease the tube pan — angel food cake needs to cling to the sides as it rises.
Sift together the flour, sugar, and salt into a large bowl. Set aside.
In a separate small bowl, whisk the egg whites until foamy. Add cream of tartar and beat on medium-high speed for about 1 minute. Gradually add the remaining sugar (the 3/4 cup from step 2) in a slow stream while beating. Continue beating until stiff peaks form — when you lift the beater, the peak should hold its shape without curling over. This takes about 5-7 minutes with an electric mixer.
Fold in the orange zest and vanilla extract using a rubber spatula, gently but thoroughly. You want to incorporate everything without deflating too much of that air you just whipped into the whites.
Pour the batter into your ungreased tube pan and smooth the top with a spatula. Bake for 38-42 minutes, until the top is golden brown and springs back when lightly pressed. The cake should pull away slightly from the sides of the pan.
Critical step: Immediately invert the pan onto its legs or a bottle neck and let it cool completely upside down — at least 1 hour. This prevents collapse.
While the cake cools, combine sliced strawberries with sugar, lemon juice, and orange juice in a bowl. Toss gently and set aside for at least 20 minutes to let the berries macerate and release their juices.
To unmold: run a thin knife around the outer edge and along the tube. Lift the cake out by gripping it from underneath with your hands — or use two forks to hook under the bottom rack of the pan if yours has one. Slice into wedges.
Serve with macerated strawberries on top, spooning extra juices over each slice. The cake is good at room temperature for up to 2 days in an airtight container.
