Preheat the oven to 180°C (356°F).
Wash the yuzu thoroughly and slice the peel thinly.
Finely chop the yuzu flesh and mix it with sugar to make yuzu syrup.
In a bowl, combine cake flour, almond flour, sugar, and salt.
Cut cold butter into small pieces, add to the bowl, and rub together with fingertips until crumbly.
Spread the yuzu syrup on the bottom of a baking pan, then top with the crumble dough.
Bake in the preheated oven for 25 minutes.
Cool and serve on a plate.