Preheat and prepare — Heat oven to 180°C (160°C fan). Grease and line a 22cm springform tin; the paper should sit snug with no folds.

Cream butter and sugar — Beat until pale and fluffy. It should look lighter in color and feel airy, not grainy.

Add eggs gradually — Whisk in one at a time. If it looks slightly split, keep whisking—it will smooth out.

Fold in dry ingredients — Add ground almonds, zest, flour, and baking powder. Mix gently until smooth and thick.

Layer first batter — Spread half into the tin, pushing it evenly to the edges to avoid uneven rising.

Add first rhubarb layer — Arrange pieces neatly, avoiding the edges. Sprinkle with 1 tablespoon sugar.

Top with remaining batter — Spread carefully to cover the fruit without dragging it around.

Finish with rhubarb and almonds — Arrange remaining rhubarb in a loose pattern, scatter almonds, and sprinkle sugar.

Bake until golden — Bake 1 hour; the top should be golden and fragrant. Cover with foil and bake another 10–15 minutes until firm in the center.

Cool properly — Let it sit in the tin until warm, then transfer. Cutting too early can make it crumble.