Preheat the oven to 190°C (375°F). Grease a 30 x 20 cm (12 x 8 in) baking tray with a 2 cm (¾ in) lip. Line the tray with sheet of baking paper, exactly the same size as the base. Spray the paper with some canola oil.
Place the eggs, half the vanilla seeds and the lemon zest in