Place a rack in middle of oven; preheat to 350°. Brush pan with vegetable oil, making sure to coat sides all the way to the rim. Line bottom of pan with a parchment paper round; brush parchment with oil.
Heat 10 oz. (283 g) semisweet chocolate (64%–70% cacao), coarsely chopped, 6 Tbsp. grapeseed, avocado, or other neutral oil, ¼ cup strong brewed coffee, and 1½ tsp. Diamond Crystal or ¾ tsp. Morton kosher salt in a large heatproof bowl set over a medium saucepan of gently simmering water (bowl should not touch water), stirring occasionally with a heatproof rubber spatula, until chocolate is melted and mixture is smooth, about 5 minutes. Remove bowl from heat; add 5 large egg yolks, room temperature, 2 tsp. vanilla extract, and ¼ cup (50 g) granulated sugar and vigorously whisk to combine. Add ¾ cup (72 g) almond flour or almond meal and mix well. (Don’t worry if it looks broken and separated.) Add ¼ cup water and whisk vigorously until mixture comes back together and looks smooth and glossy. Set chocolate mixture aside.
Using an electric mixer on medium-low speed, beat 5 large egg whites, room temperature, and a pinch of salt in a large non-plastic bowl until frothy, about 20 seconds. Increase speed to medium-high and continue to beat until foamy and opaque, about 30 seconds. Beating constantly, gradually add remaining ¾ cup (150 g) granulated sugar in a slow, steady stream. Increase speed to high and beat until stiff peaks form and meringue is dense and glossy. (Be careful not to overbeat or it will be dry and grainy and difficult to incorporate into the batter.)
Scoop out a heaping cupful of meringue and set aside. Scrape about half of the remaining meringue into bowl with reserved chocolate mixture and fold gently with spatula until just a few streaks remain. Scrape in the rest of the meringue; fold just until evenly mixed and batter is light and airy. Scrape batter into prepared pan; smooth surface. Spoon dollops of reserved meringue over batter. Using a skewer or toothpick, swirl into batter—a little or a lot; it’s up to you.
Bake cake until surface is risen and cracked, meringue is light golden, and a tester inserted into the center comes out shiny but clean, 60–70 minutes. Transfer to a wire rack and run a small knife or offset spatula between very top of cake and pan to loosen anywhere it may be stuck (this will help the cake settle evenly as it cools). Let cake cool in pan.
To serve, run knife around sides again to loosen cake, then unmold.