Heat the oven to 200C / 390F for a standard oven or 180C / 350F for fan / convection, then grease a 22 cm / 9 inch springform pan with butter and line the base with baking paper. The prepared pan should be ready before the batter is mixed so the baking powder can go straight to work once combined.
Rinse the blueberries and shake off the extra water without patting them dry, then set aside about one-third for the top and toss the rest with the flour. The light flour coating helps the berries cling to the batter, and the topping portion gives the finished cake a more berry-packed surface.
Whisk the sugar, oil, eggs, grated lemon rind, lemon juice, and yoghurt in a large bowl until smooth and evenly blended. The mixture should look glossy and pale yellow, with the lemon zest flecked throughout and a fresh citrus scent rising from the bowl.
Add the flour and salt, then sprinkle the baking powder over the top and whisk only until the batter comes together. The batter should look thick and slightly lumpy rather than silky, which is exactly what helps hold the fruit in place.
Fold in the floured blueberries along with any loose flour left in the bowl, then scrape the batter into the pan and scatter the reserved berries over the top. The fruit should be evenly distributed, and the batter will feel substantial enough that the top berries sit on the surface instead of sinking immediately.
Place the pan on the lower-middle rack, reduce the oven to 180C / 350F for a standard oven or 160C / 320F for fan / convection, and bake for 50 minutes. The cake is ready when a skewer comes out clean and the kitchen smells strongly of lemon with sweet berry notes.
Remove the springform sides, cool the cake on a rack, and once fully cool, remove the base before dusting with icing sugar and serving. The crumb sets as it cools, so waiting gives you neater slices and keeps the fruit pockets from tearing.