Makes one 8 1/2 -x-4 1/2 -inch (2 L) loaf.
Preheat the oven to 350ºF (180ºC). Grease and flour a 8 1/2 -x-4 1/2 -inch loaf tin and line the bottom and sides (just the long sides is fine) of the pan with parchment paper so that the paper comes over the sides.
Measure the sugar into a large mixing bowl and finely zest the lemons into it, whisking to stir in the zest (this draws out the oils). Whisk in the eggs, followed by the cream, oil and vanilla.
Sift the flour, baking powder and salt over the bowl and whisk until the batter is smooth. Gently stir in the blueberries and then pour this into the prepared pan and bake for 60-70 minutes, until a tester inserted in the centre of the cake comes out clean. Cool the cake for 20 minutes in the tin before removing to cool on a rack.
For the icing, whisk the lemon juice into the icing sugar by hand until smooth and flowing. Pour this over the cooled loaf and let a little drip over the sides. The loaf can be sliced right away, but letting it sit for an hour allows the glaze to set up for tidier slicing.
The loaf will keep, well-wrapped on the counter for up to 4 days.