Please read About High-Altitude Cake Baking and About Butter Cakes. This recipe is for baking at 5,000 through 7,000 feet. At 10,000 feet, reduce the oven heat to 350°F. Reduce the butter by 2 tablespoons (30g), use only 7 yolks, and reduce the sugar beaten into the yolks by 2 tablespoons (25g). Increase the flour by 2 ⅓ tablespoons (20g) and the cream of tartar by ½ teaspoon. Bake 25 to 30 minutes, then (without cooling first) immediately invert onto a rack, unmold, and cool completely.

Have all ingredients at room temperature, about 70°F. Preheat the oven to 375°F. Grease a 10-inch Bundt pan generously and dust with flour; tap out excess flour.

Combine in a medium bowl:

Sift together and return to the sifter:

Beat in a large bowl, or in a stand mixer with the whisk attachment, until foamy:

Gradually add and beat on high speed until soft, slightly droopy peaks form:

Beat in another large bowl (or transfer the egg whites to another bowl and reuse the stand mixer bowl and the whisk) on high speed until the batter is thick and a pale lemony color and forms a continuous flat ribbon when dropped from the beaters:

Reserve about 1 ½ cups of the egg whites. Fold the remaining whites into the batter in 2 additions alternating with the flour in 2 additions (sift the flour on top and then fold in). Stir the melted butter–lemon juice mixture and fold into the reserved whites; try to maintain volume in the whites while blending in the liquid. Fold the lemon mixture into the batter; make sure no liquid pools in the bottom of the bowl. Scrape the batter into the pan and run a knife through the batter once to release any large air bubbles. Bake until a cake tester inserted into the center comes out clean, 20 to 25 minutes.

Let cool in the pan on a rack for about 10 minutes. Run a knife between the cake sides and tube, top with a plate, invert, and unmold. Let cool completely.

Just before serving, sprinkle with:

Slice with a serrated knife.