FOR SAUCE: In a blender, combine raspberries, sugar and 1 tablespoon water; purée until smooth. Set aside sauce.

FOR CAKE: Heat oven to 350º with rack in middle. Lightly grease a 10-inch springform pan with butter and dust with flour.

In the bowl of an electric mixer fitted with the whisk attachment, beat together eggs, 2/3 cup sugar, vanilla and pinch salt on high speed until light and frothy.

Using a rubber spatula, very gently fold flour into batter, then scrape batter into prepared pan; place pan on a baking sheet. Bake, rotating halfway through, until cake Is golden and a cake tester comes out clean, 20 to 25 minutes. 

Transfer cake pan to a wire rack and let cool 10 minutes, then release cake from pan and let cool completely. Cut cake into 1/3-inch-wide strips.

In a small bowl, whisk together liqueur and 2 tablespoons water. Brush ⅓ of liqueur mixture on the bottom of an ovenproof plate or inverted cake pan (at least 10 inches, but small enough to fit in your freezer). Arrange 1 layer of cake strips, cut-side down, on the plate, using long and short pieces as needed to create a circular shape. Brush with half of the remaining liqueur.

Cover cake strips with scoops of gelato. When gelato is slightly warmed, 1 to 2 minutes, use a spatula to spread evenly over the cake, mounding slightly in the center, then top with remaining cake strips. Brush cake with remaining liqueur mixture. Freeze at least 40 minutes or overnight.

Heat oven to 500º with rack in middle.

In the bowl of an electric mixer fitted with the whisk attachment, beat egg whites and pinch salt on medium speed until white and frothy. With machine running, slowly add remaining 1/3 cup sugar, then increase speed to medium-high and beat until stiff peaks form. 

Transfer meringue to a pastry bagfitted with a decorative tip, if using. Transfer frozen cake (still on plate or inverted cake pan) to a baking sheet lined with parchment or wax paper. Pipe or spread meringue over cake. Alternatively, mound meringue over cake, spreading to edge of pan to cover completely.

Place in oven and cook until meringue is lightly browned, 2 to 3 minutes. Carefully transfer cake to a serving plate using
2 metal spatulas. Serve immediately with reserved raspberry sauce.