Have the blueberry curd made and cooled before starting the cake batter. The curd can be made up to a week ahead of time.
Preheat the oven to 350 F. Grease and flour an 8 inch round baking pan (8 inch square works too).
Set the sugar and salt in the bowl of a mixer (or use a hand mixer) and zest the lemon over it. Rub the lemon zest into the sugar to release its oils.
Add the butter and beat (using the paddle attachment) until the mixture is creamed, about 3-5 minutes - stopping to scrape the bowl halfway to ensure an even mix.
Add the eggs and beat until airy, about 2 minutes.
Add the flour, baking powder and almond meal and mix to just combine - don’t overmix the batter.
Spread the batter into the bottom of the prepared pan, smoothing it out.
Dollop 4-5 heaped tablespoons of blueberry curd over the batter and spread them so they cover most of the cake batter but avoid the outer rim/edge of the cake. I leave a small circle of batter uncovered with curd so I can use a cake tester to know when it’s done baking. Sprinkle granulated sugar over the bits of exposed cake batter.
Bake the cake until a cake tester comes out clean of wet crumbs (test in the center of the cake), about 30-40 minutes. Let cool in the pan then transfer to a plate. Note: This cake will sink due to the weight of the thick, liquid curd. Store the cake in the fridge, serve cold or at room temperature.