Step 1

Position a rack in the center of the oven and preheat to 350ºF. Rub an 8- or 9-inch round springform pan with a bit of olive oil.

Step 2

Place the chocolate, oil and salt in a large, metal bowl. Place the bowl in a skillet filled with 2 inches of barely simmering water, and stir frequently until the chocolate is melted.

Step 3

Remove the bowl from the skillet and whisk in ½ cup of the sugar, then whisk in the egg yolks.

Step 4

Place the egg whites and cream of tartar in the bowl of a stand mixer fitted with the whisk attachment. Whip on medium-high speed until foamy, then gradually pour in the remaining ¼ cup of sugar, whipping the whites until they hold soft peaks (i.e., when you pull the whisk out and hold it upside down, the peaks of white flop over).

Step 5

Without delay, use a flexible spatula to stir one-third of the whipped whites into the chocolate mixture.

Step 6

Add the remaining whipped egg whites to the bowl, sift in the almond and sweet rice flours, and gently fold until the batter is just combined and no streaks remain.

Step 7

Immediately scrape the batter into the prepared pan, and smooth the top. Bake the cake until a toothpick inserted in the center comes out with moist crumbs, 30-40 minutes.

Step 8

Let the cake cool completely, then remove the sides of the pan. Dust with cocoa powder just before serving if you wish, then use a large chef's knife wiped clean after each cut to slice the cake.

Step 9

If you like, serve the cake with a dollop of cream, a drizzle of olive oil, a few flecks of flakey salt, and/or seasonal fruit or berries.

Step 10

The cake will keep, covered at room temperature, for up to three days. Refrigerate or freeze for longer storage.