Preheat your oven to 170°C (340°F). Line a loaf pan with parchment paper, leaving extra overhang for easy removal.
In a clean mixing bowl, whisk the egg whites and cream of tartar until foamy. Continue to whisk until soft peaks form.
Slowly drizzle in the honey and vanilla extract while whisking, continuing until stiff, glossy peaks are achieved and the mixture feels thick and smooth.
In a separate bowl, combine the sifted flour and melted butter. Mix gently until just incorporated.
Gently fold one-third of the whipped egg whites into the flour mixture to lighten it, then carefully fold in the remaining egg whites, taking care not to deflate the batter.
Pour the batter into the prepared loaf pan, smoothing the top with a spatula for an even surface.
Bake in the preheated oven for about 40 minutes, or until the top is golden brown and a skewer inserted into the center comes out clean.
Remove the cake from the oven and let it cool in the pan for 10 minutes, then lift it out using the parchment overhang and transfer to a wire rack to cool completely.
Slice the cake once cooled, revealing its airy, light crumb and golden crust. Enjoy plain or with a light dusting of powdered sugar.
