Beat the eggs and sugar together until the mixture reaches a ribbon consistency (thick and falls slowly from the whisk).
Add vanilla extract, then gently fold in the cake flour, saffron, and cardamom powder.
Finish by folding in the melted butter, then gently fold in the crumbled chenna.
Pour the batter into a 24 × 32 cm / 9½ × 12½ in baking pan lined with aluminum foil.
If using a professional Rational oven, bake on sponge mode for 16 minutes.
If using a conventional oven, preheat to 160 °C / 320 °F and bake for 20 minutes.
Transfer the sponge to a cooling rack, allow to cool completely, then refrigerate.
Once chilled, cut into 2¼-inch (about 6 cm) circles.