Line three 8-inch cake tins with parchment paper, and heat the oven to 350F.
Whip the egg whites with the salt until they form stiff peaks.
In a separate bowl, beat the egg yolks, sugar and lemon rind together with the lemon extract until they become voluptuously creamy.
Beat one-third of the flour into the egg yolks, then fold in one-third of the egg whites. Continue working the flour and egg whites into the batter one-third at a time, until they're fully incorporated, taking care not to deflate the egg whites too much.
Distribute the batter evenly among three pans, and bake the cakes until the center is set and springs back when you touch them - about 35 to 30 minutes. Cool the cakes in their pans for 5 minutes, and then turn them out onto a wire rack to continue cooling.
For the Frosting
Toss the frozen raspberries, honey and lemon juice into a saucepan. Bring berries to a boil over medium-high heat, allowing the raspberries to release their liquid. Continue boiling the raspberries until thickened to a jam-like consistency, about ten minutes.
Set a fine-mesh sieve over a bowl, and pour the raspberries into the sieve, pressing down to strain as much juice away from the seeds as possible, until you have about ¾ cup strained raspberry juice. Reserve both the raspberry juice and the pulpy seeds separately, allowing them to cool in the fridge.
In a stand mixer fitted with a wire whisk, whip the mascarpone with the heavy whipping cream, slowly drizzling in the strained raspberry puree, until the frosting is fully whipped, fluffy and thoroughly pink with no pockets of juice remaining.
To frost the Cake
Set a single layer of cake on your cake stand, and top it with one-half of the reserved, seeded raspberry puree. Set a second layer of cake on top of the first, and spread it with the remaining seeded raspberry puree. Place a third layer of cake over the second, and then frost the cake as you normally would with the Raspberry Cream Frosting.
The cake will keep up to 3 days, refrigerated, and overnight without refrigeration.
Notes
Change up your flours! You can make this cake using sprouted flour and whole, white wheat pastry flour, too! Change up your sugar! You can substitute whole, unrefined cane sugar as well as coconut sugar for the granulated sugar in this recipe on a 1:1 ratio; however, your cake's crumb will be darker than the cake shown here.