Beat the sugar and eggs together, then add the oil, milk, lemon zest, and finally the baking powder, forming a smooth and creamy batter. Bake at 180°C (356°F) for 20 minutes. In a saucepan, sift the sugar and cornstarch, add the lemon zest, and gradually stir in the water. Cook over low heat until thickened (this will only take a few minutes).

Once off the heat, add the lemon juice, stir, then incorporate the butter. The consistency will be like a spread, and it may solidify as it cools—but you can gently reheat it in a double boiler if necessary (although this step won’t be needed if your base is ready). Unmold the base, spread the gelée cream over it evenly with a spatula or spoon. Place the egg whites, salt, and the tablespoon of sugar in a stand mixer. Separately, heat the water and remaining sugar without caramelizing it.

It should become a light and clear syrup (it’s ready when bubbles appear). Whisk the egg whites for 1 minute, then slowly drizzle in the hot syrup while beating, until stiff peaks form and the bowl cools. Once the meringue is ready, pipe small dollops onto the tart and use a torch to lightly brown the surface.