Adjust an oven rack to the lower-middle position and heat oven to 325 degrees. Have ready an ungreased large tube pan (9-inch diameter, 16-cup capacity), preferably with a removable bottom. If the pan bottom is not removable, line it with parchment or wax paper.

In a small bowl, whisk the flour with 3/4 cup sugar. Place remaining 3/4 cup sugar in another small bowl next to the mixer.

In the bowl of a standing mixer, or with a handheld mixer, beat egg whites at low speed until just broken up and beginning to froth. Add cream of tartar and salt and beat at medium speed until whites form very soft, billowy mounds. With the mixer still at medium speed, beat in 3/4 cup sugar, 1 tablespoon at a time, until all sugar is added and whites are shiny and form soft peaks. Add vanilla, lemon juice, and almond extract and beat until just blended.

Place flour-sugar mixture in a sifter set over waxed paper. Sift flour-sugar mixture over egg whites about 3 tablespoons at a time, and gently fold it in, using a large rubber spatula. Sift any flour-sugar mixture that falls onto the paper back into the bowl with the whites.

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 the cake is golden brown and the top springs back when pressed firmly, 50 to 60 minutes.

If cake pan has prongs around the rim for elevating the cake, invert pan onto them. If not, invert pan over the neck of a bottle or funnel so that air can circulate all around it. Let the cake cool completely, 2 to 3 hours.

To unmold, run a knife around edges, being careful not to separate the golden crust from the cake. Slide cake out of pan and cut the same way around removable bottom to release, or peel off parchment or wax paper, if used.

Place the cake, bottom-side up, on a platter. Cut slices by sawing gently with a serrated knife. Serve the cake the day it is made.