Step 1Heat the oven to 350 degrees. Generously grease the interior of two 9-inch round cake pans, both bottom and sides, with butter. If possible, line the bottom of each pan with a 9-inch round of parchment or wax paper and grease it also.
Step 2Sprinkle about 2 teaspoons flour into each pan and shake around until each interior is thoroughly dusted. Turn the pans upside down over the sink and tap against the sink to dislodge any excess flour.
Step 3In a medium mixing bowl, stir 3 cups flour with the baking powder and salt and set aside. In a measuring cup or small bowl, combine the milk with the vanilla and set aside.
Step 4In the bowl of a stand mixer, or in a large bowl using an electric mixer, beat the 1 cup butter until fluffy, 1 to 2 minutes.
Step 5Reduce the speed and add the sugar with the mixer running, continuing to mix until light and fluffy, 2 to 3 minutes more. Add the eggs one at a time and beat into the mixture.
Step 6Add one-third of the milk mixture and beat until absorbed. Add one third of the flour mixture and beat just until the flour is absorbed. Repeat with the remaining milk and flour in two batches.
Step 7Divide the batter between the two cake pans and smooth the tops with a spatula. Bake the cakes in the center of the oven until the tops are golden brown and the cake starts to pull away from the sides of pan, 25 to 35 minutes.
Step 8Remove the cake pans from the oven and set on a cooling rack or folded towel for 10 minutes. Overturn the cake pans onto a rack or plate, remove the pans and paper from them and return the layers, right-side up, to the rack or towel. Wait to frost the cakes until they have cooled to room temperature.
Step 1Puree the raspberries in a food processor and force through a strainer to remove the seeds. This should make about one-half cup raspberry puree. Stir in 6 tablespoons sugar until dissolved and set aside.
Step 2In a medium bowl, combine the remaining sugar, corn syrup and water mixture, egg whites, salt and cream of tartar. Beat the contents with a hand-held electric mixer until lightly foamy and pale yellow, about 1 minute.
Step 3Place the bowl over a larger pot of simmering water (making sure the bottom of the bowl does not touch the water). Continue to beat the mixture to achieve a puffed and billowy white meringue (the meringue will practically reach the top of the mixer blades), 8 to 10 minutes. Continue beating until the mixture holds stiff peaks and just begins to lose its gloss, 1 to 2 minutes more.
Step 4Remove the bowl from the pot of simmering water and add the vanilla. Beat one additional minute to fully incorporate the vanilla.
Step 5Assemble the cake: Put one cake layer, top side down, on a serving plate or stand. Cover the top with about one-third of the frosting, then drizzle over one-third of the raspberry puree. Set the second layer, top-side up, over the first. Frost the top and sides of the cake with the remaining frosting, and drizzle over the remaining raspberry glaze. Serve immediately.