Center a rack in the oven and preheat the oven to 150 C (300 F). Butter two 8 x 2 inch round cake pans and line the bottom of each pan with a round of buttered parchment or wax paper. Put the pans on a baking sheet.

For the cake layers:

Sift together the flour, baking powder and salt.

Whisk together the milk and egg whites in a medium bowl. Put the sugar and lemon zest in a mixer bowl or another large bowl and rub them together with your fingers until the sugar is moist and fragrant

Add the butter and beat at medium speed for a full 3 minutes, using either a hand-held mixer or a stand mixer

The butter and sugar should become very light

Beat in the extract, then add one third of the flour mixture, still beating on medium speed

Beat in half of the milk-egg mixture, then beat in half of the remaining dry ingredients until incorporated

Add the rest of the milk and eggs beating until the batter is homogeneous, then add the last of the dry ingredients

Give the batter a a final beating to ensure that it is thoroughly mixed and well aerated

Divide the batter between the two pans and smooth the tops with a rubber spatula

Bake for 40 minutes minutes, or until the cakes are well risen and springy to the touch - a skewer inserted into the centers should come out clean

Transfer the cakes to cooling racks and cool for about 5 minutes, then run a knife around the sides of the cakes, unfold them and peel off the paper liners. Invert and cool to room temperature, right side up (the cooled cake layers can be wrapped airtight and stored at room temperature overnight or frozen for up to two months).

To make the cranberry buttercream:

Set a saucepan filled one-third full of water over medium-high heat and bring to a simmer.

Whisk together the egg whites, sugar, and salt in a large heatproof bowl. Set over the simmering water and whisk until the mixture is hot to the touch and the sugar has dissolved.

Transfer the mixture to a large metal mixing bowl. Use a stand mixer of best results. I use a hand-held mixer, which takes around 30 minutes to whip the buttercream until it is set.

Beat on low speed for 2 minutes. Increase to medium-high until stiff peaks are formed.

Continue beating at medium-high speed until the mixture is fluffy and has cooled (the mixing bowl should feel cool to the touch).

On medium-low speed, add the butter, a few cubes at a time, beating until well incorporated before the next addition. The buttercream will appear to curdle, which is normal. This happens because the the butter 'shocks' the meringue when it is added.

Add the vanilla extract and the cranberry jam or syrup, and food coloring, if desired. I added a couple of drops of gel food coloring.

Beat until the frosting is thick and completely smooth.

To Assemble:

Using a serrated knife, slice each cake layer in half to get 4 layers.Spread a heaped teaspoon of cranberry jam over one layer, and smooth it out using an off-set spatula. Over this pipe out some buttercream and spread this with a spatula. Cover with the next layer of cake. Repeat with the next three layers. Using an offset spatula and a turntable to frost the edges neatly. Optionally, top the cake with some crushed meringue for texture. I used raspberry flavored macarons, which I crushed and sprinkled on top of the cake.