Preheat the oven to 350 degrees.

Generously butter a 9-inch springform pan.

Into a medium bowl, sift together the flour, baking powder, and salt. Set aside.

In a large bowl, beat the egg yolks with an electric mixer on high for 3 minutes. Then, with the mixer still running, gradually add 1/3 cup of the sugar, and continue beating until thick light-yellow ribbons form in the bowl, about 5 minutes more.

Beat in the vanilla and lemon extracts.

Sift the flour mixture over the batter, and stir it in by hand until no more white flecks appear. Then blend in the butter.

In a clean bowl, using clean dry beaters, beat the egg whites and cream of tartar together on high until frothy. Less than a tablespoon at a time, add the remaining 2 tablespoons of sugar and continue beating until stiff peaks form.

Stir about 1/3 cup of the whites into the batter, then gently fold in the remaining whites (don’t worry if a few white specks remain).

Gently spoon the batter into the pan.

Bake the cake just until the center springs back when lightly touched, only about 10 minutes (watch carefully). Let the cake cool in the pan on a wire rack while you continue making the cheesecake filling. Do not remove the cake from the pan.