Adjust an oven rack to the lower-middle position. Heat oven to 375 degrees. Set aside an un-greased tube pan (9 1/2 inch or 10 inch, 12 cup capacity) with a removable bottom.
In a food processor or blender, pulse the sugar until powdery and fine. Remove 1 cup and set aside, leaving the rest in the food processor. Add the flour and salt to the food processor and pulse until mixture is aerated and light, about 5 to 10 pulses.
In a standing mixer fit with the whisk attachment, or with an electric mixer by hand, on low-speed beat egg whites and cream of tartar until broken up and beginning to froth, about 1 minute.
Increase speed to medium. Slowly add the reserved 1 cup of sugar and beat until whites are glossy and forming very soft peaks, about 5 to 6 minutes. Add lemon juice, vanilla extract, and almond extract and beat just until incorporated.
Carefully fold in sifted flour and sugar mixture into the egg whites using a large spatula. Gently scrape batter into pan, smooth the top, and give pan a couple of gentle shakes on the counter to release any large air bubbles.
Bake until cake is golden brown and the top springs back when pressed firmly, about 40 minutes.
Remove from oven. If cake pan has feet, invert pan onto them. If not, invert pan over the neck of a bottle so that air can circulate all around it. Allow to cool completely, about 2 to 3 hours.
To un-mold, run a knife or thin spatula around edges, being careful not to dislodge the golden crust. Pull cake out of pan and cut the same way around removable bottom under the cake to release.
Cool cake completely, bottom side up. When completely cold, cut slices by sawing gently with a serrated knife or pulling with a taut thread through the cake.
Serve cake the same day or refrigerate in an airtight container overnight if serving the next day. (Cake may be frozen for up to 2 weeks, but will compress slightly.)