Heat the oven to 375°F. Line a loaf pan with parchment and grease it with coconut oil. Separate the six eggs into yolks and whites, keeping the whites in a clean, grease-free bowl.

Mix the yolks, four tablespoons melted coconut oil, measured hazelnut flour and sea salt until evenly combined. If this mixture is too stiff to mix, loosen it with a little of the still-unwhipped white from these same six eggs. Do this before beating the remaining whites.

Whip the remaining egg whites until stiff peaks form: the lifted whisk leaves a peak that stands upright. The whites should look foamy and hold their shape. Have the yolk mixture and pan ready so the whipped whites do not sit waiting.

Fold the yolk mixture into the whipped whites gently but promptly. Lift batter from underneath and turn it over until the color is even and no white streaks remain. Stop once combined; beating or repeatedly stirring it will knock out the trapped air.

Transfer the airy batter to the prepared pan and smooth the top gently. Leave about one inch below the rim. If there is extra batter, put it in a small greased oven-safe custard cup rather than overfilling the loaf pan. Dust lightly with extra hazelnut flour if desired.

Bake for 25–35 minutes, until a knife inserted into the center comes out clean. Look for a set top rather than a liquid-looking middle. Check any separate small cup on its own endpoint; it is smaller than the loaf.

Rest the loaf in its pan for five minutes. Remove it from the pan, peel away the parchment and leave it on a metal rack until completely cool. Slice the cooled loaf into ten slices.