Adjust an oven rack to the lower-middle position. Heat oven to 325 degrees. Set aside an un-greased tube pan (9 1/2 inch or 10 inch, 12 cup capacity) with a removable bottom.
In a small bowl, sift together flour and 3/4 cup sugar. Stir vigorously with a whisk to incorporate as much air as possible. Set aside.
In a standing mixer fit with the whisk attachment, or with an electric mixer by hand, on low speed beat egg whites until broken up and beginning to froth, about 1 minute.
Increase speed to medium. Add cream of tartar and salt and beat until whites form very soft peaks, about 12 to 15 minutes.
With the mixer still at medium speed, beat in remaining 3/4 cup sugar, 1 tablespoon at a time, until all sugar is added and whites are shiny and form soft peaks, about 5 minutes.
Add vanilla, lemon juice, and almond extract and beat until just blended.
Carefully fold in sifted flour and sugar mixer into the egg whites using a large spatula. Gently scrape batter into pan, smooth the top, and give pan a couple of raps on the counter to release any large air bubbles.
Bake until cake is golden brown and the top springs back when pressed firmly, about 50 to 60 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 freeze overnight if serving the next day. (Cake may be frozen for up to 2 weeks, but will compress slightly.).