Heat the oven to 170 C / 340 F. Butter a 23 cm / 9-inch springform or loose-bottom tart pan.

Spread the almonds on a sheet pan and toast for 6 to 8 minutes until fragrant. Cool slightly, then chop roughly, leaving some pieces larger than others.

In a large mixing bowl, whisk together the cornmeal, flour, sugar, salt, and lemon zest.

Add the cold, cubed butter. Rub it into the dry mix with your fingertips until it looks like coarse, uneven gravel, some bits pea-size, some finer. Don't work it into a smooth dough.

Add the toasted almonds, egg yolks, and grappa if using. Mix briefly with a fork just until combined, the mixture should stay loose and crumbly, never forming a ball.

Scatter the crumbly mixture into the prepared pan in an even layer. Press lightly, just enough to compact the base, keeping the surface craggy and uneven.

Scatter the reserved almonds over the top for texture and looks.

Bake for 35 to 40 minutes, until deep golden brown and firm to the touch at the edges.

Cool completely in the pan on a wire rack, at least 1 hour, before releasing the sides and breaking or cutting into wedges.

Dust with powdered sugar just before serving.