Pour the water into a small pot, then stir in the sugar until blended.

Gently heat the mixture on a low flame, stirring now and then until the sugar melts completely into the liquid.

When it's ready, take it off the stove and allow it to cool down naturally until it reaches room temperature.

Preheat your oven to 350°F (175°C).

Coat two 9-inch round cake pans with a thin layer of oil or butter, then dust them with a bit of flour to help prevent sticking. You may also line the bottoms with parchment and grease that too.

In a bowl, sift the cake flour, baking powder, and a pinch of salt together to ensure they are well combined and to add lightness to the mixture.

In another bowl, whisk together the buttermilk and egg whites until well blended.

In a mixing bowl, rub the lemon zest into the sugar using your fingers until fragrant.

Mix the softened butter with the sugar and whip them together on medium speed for about five minutes, until the texture becomes smooth and airy.

Blend in the vanilla extract.

Gradually incorporate the dry ingredients in three parts, alternating with the milk-egg mixture. Begin and end with the dry mix.

Beat the batter for an extra 1–3 minutes to ensure it’s fully combined and smooth.

Divide the batter evenly into your prepared pans.

Bake the cakes for 30 to 40 minutes, or until a toothpick poked into the middle comes out without any wet batter.

Let cakes cool in the pans for 5 minutes, then turn out onto wire racks. Remove parchment if used and let them cool completely.

Grate the lemon peel for zest and squeeze out the juice, placing each in separate bowls for later use.

In a bowl, whisk together the egg yolks and sugar until smooth.

Stir in the lemon zest and juice.

Transfer to a saucepan and cook over medium heat until the mixture begins to bubble.

Lower the heat and keep stirring until the mixture becomes thick enough to cling lightly to the back of your spoon.

Pour the curd through a fine mesh strainer into another bowl to remove any lumps and create a smooth finish.

Add the chilled butter, one tablespoon at a time, stirring after each addition until the mixture becomes smooth and creamy.

Place plastic wrap directly on the surface and refrigerate until completely chilled.

Sprinkle the gelatin over a few tablespoons of water and let it bloom for 3 to 5 minutes.

Warm the simple syrup in a saucepan and stir in the gelatin until fully dissolved. Let cool slightly.

Whip the heavy cream in a cold bowl until stiff peaks form. Transfer to a separate bowl and chill.

In the same bowl, beat together the cream cheese and lemon curd until creamy.

Slowly drizzle in the cooled gelatin mixture while beating, scraping the bowl as needed.

Fold in the whipped cream gently and chill until the mixture thickens.

In another bowl, mix the flour and powdered sugar thoroughly until well blended.

Use a fork or pastry blender to cut the cold butter into the flour mixture until it forms small, uneven crumbs.

Add the vanilla, stir to combine, and refrigerate until ready to use.

Once cake layers are completely cool, brush each layer with the remaining simple syrup for extra moisture.

Spread about two-thirds of the filling over the bottom cake layer.

Place the second layer on top and use the remaining filling to frost the top and sides.

Sprinkle or press the vanilla crumble on the top (and sides, if desired).

Chill for several hours to firm up, or freeze briefly if you’re in a hurry.