Step 1

Heat the oven to 325°F with a rack in the lower-middle position. Mist a 9-inch springform pan with cooking spray. In a small bowl, whisk together the flour, baking soda and salt.

Step 2

In a medium saucepan over medium, bring about 1 inch of water to a simmer. Put the chocolate in a heatproof large bowl and set the bowl on top of the saucepan; be sure the bottom does not touch the water. Stir occasionally until the chocolate is completely melted. Remove the bowl from the pan. Add the oil, cocoa, espresso powder and 107 grams (½ cup) sugar; whisk until well combined. Add the egg yolks and lemon juice; whisk until smooth. Add the dry ingredients and gently whisk until fully incorporated.

Step 3

In a stand mixer with the whisk attachment or in a large bowl with a hand mixer, whip the egg whites on medium-high until frothy, 1 to 2 minutes. With the mixer running, gradually add the remaining 107 grams (½ cup) of the sugar, then beat until the whites hold soft peaks, 1 to 2 minutes. Add about one-third of the whipped whites to the yolk-chocolate mixture and fold with a silicone spatula to lighten and loosen the base. Scrape in the remaining whites and gently fold in until well combined and no white streaks remain; the batter will be light and airy.

Step 4

Gently pour the batter into the prepared pan and smooth the surface. Bake until well risen, the surface is crusty and a toothpick inserted into the center of the cake comes out with a few crumbs attached, 45 to 50 minutes; do not overbake.

Step 5

Set the pan on a wire rack and immediately run a narrow-bladed knife around the edge of the cake to loosen the sides. Cool in the pan for at least 1 hour before serving; the cake will deflate as it cools. When ready to serve, remove the pan sides and, if desired, dust with cocoa.