Heat the oven to 350 degrees F. Spray an 8x6-inch baking pan (or pan of similar size) with cooking spray
Mix the flour and baking powder in a medium bowl. Set aside.
In a large mixing bowl, using an electric mixer, whip the egg whites until frothy. With the mixer running, gradually add the sugar and beat to soft peaks.
Beat in the egg yolks, one at a time, blending well after each addition.
Add the flour mixture in 3 additions, alternating with the milk in 2 additions. Add 1 tablespoon of limoncello and stir until just combined.
Pour the batter into the lightly greased pan and bake until a toothpick inserted in the center, comes out clean, 25- 30 minutes. Remove the cake from the oven and let it cool slightly on a baking rack for about 10 minutes.
Pierce the top of the cake all over with the tines of a fork or a thick skewer.
Mix the sweetened condensed milk, evaporated milk, 1/2 cup of the heavy cream, and 1 1/2 tablespoons of the limoncello in a medium bowl. Pour the mixture over the cake while warm. Cover and refrigerate a least 3 hours or overnight.
When you are ready to serve the cake, combine the remaining 1/2 cup heavy cream, powdered sugar, and the cinnamon in a medium bowl. Using an electric mixer, beat the cream until soft peaks form. Spread the whipped cream onto top of cake and sprinkle with additional ground cinnamon.