Heat the oven to 170C/150C fan/gas 3 1/2. Whisk the egg yolks in a large bowl with 20g of the sugar, the flour, oil, milk, baking powder and vanilla extract until just combined, being careful not to overmix. Set aside.

Beat the egg whites in a separate large bowl using an electric whisk (or do this in a stand mixer) until foamy. Whisk in the remaining sugar in three small additions until just combined, then add the cream of tartar. This process should take about 6-8 mins. Continue to whisk the egg whites for about 5 mins, or until the mixture holds stiff peaks and is thick and glossy.

Gently fold the whipped egg whites into the batter, a third at a time, until fully combined. Do not overmix, as you want to keep as much air in the batter as possible.

Generously oil a 20cm angel food cake tin, or a 22-23cm bundt or ring tin. Sift over some flour to coat the tin in a thin, even layer. Pour in the batter and gently tap the tin on a work surface a few times to ensure it's in an even layer. Bake for about 40 mins, or until a skewer inserted into the centre comes out clean. Invert onto a wire rack and leave it to cool completely before removing the tin. To do this, gently run a cutlery knife around the edge to loosen. Serve in wedges dusted with icing sugar, if you like.