Preheat the oven to 350°F (175°C). Grease a 9-inch springform pan and line the base with parchment if you want easy release.

In a medium bowl, whisk together the polenta, almond flour, baking powder, and salt. This mix gives your cake structure and that tender, nubby bite.

In a separate bowl, beat the butter and sugar together until pale and fluffy. This helps create a light crumb.

Beat in the eggs one at a time. Stir in the vanilla extract and lemon zest to brighten the batter.

Alternately fold the dry ingredients and almond milk into the butter mixture, starting and ending with the dry mix. Fold gently to keep the batter airy.

Fold in 1½ cups of the blueberries, saving the rest for the topping. Try not to crush the berries too much.

Spoon the batter into the prepared pan and smooth the surface. Scatter the remaining ½ cup blueberries on top and finish with a generous sprinkle of demerara sugar.

Bake for 45–50 minutes, or until the top is golden and a skewer inserted in the center comes out clean (a blueberry streak is fine).

Cool in the pan for 10 minutes, then release the springform sides and let cool completely on a wire rack. Slice and serve as-is, or with a spoonful of whipped cream or ice cream.