Preheat your oven to 325 degrees. Spray the springform pan with cooking spray, dust it evenly with flour and remove any excess.
Add the shortbread cookies, brown sugar, slivered almonds, and melted butter to the food processor. Pulse until fine crumbs form.
Add the crumb mixture to a 10-inch springform pan. Using your hands, firmly press the crumbs into the bottom of the pan. Set aside.
Drain your ricotta cheese. Place the ricotta cheese in a sieve over a large bowl. Set aside. Wash and dry the lemon. Using a zester or grater remove 1 1/2 teaspoons of lemon zest from the lemon. Place the lemon zest into a small bowl. Set aside. Next, separate your eggs. Place the whites in one small bowl and the yolks in another small bowl. Set both bowls aside.
In a stand mixer fitted with a whisk attachment, whip your egg whites on low speed until they are frothy. Add your cream of tartar. Increase the speed to medium and continue beating. When the whisk is leaving lines in the egg whites, and the meringue begins to look soft and pillowy, slowly add two tablespoons of granulated sugar into the mixture. Continue whipping until your meringue is creamy and has soft peaks. Pour the meringue in a large bowl. Set aside.
In a stand mixer fitted with a whisk attachment, add the egg yolks, and 5 tablespoons of sugar. Mix until well blended. Add the drained ricotta to your yolk mixture. Pour in the heavy cream, lemon zest, nutmeg, vanilla extract, almond extract, flour, and the remaining sugar. Mix on low to medium speed until well combined.
Next, remove the bowl from the mixer. Using a silicone spatula, gently fold in the meringue carefully not to deflate it. Pour the meringue directly over the prepared shortbread crust in the springform pan.
Place the ricotta cheesecake in the preheated oven on the middle rack for 45 to 55 minutes or until golden brown. Allow the cheesecake to cool on a wire cooling rack for 1 1/2 hours before removing from the springform pan. The cheesecake will deflate and become denser in appearance. Once the cheesecake has cooled on the counter for 1 1/2 hours, cover with plastic wrap and chill in the refrigerator for 4 hours to overnight before serving. Enjoy!
Substitute orange zest for lemon zest if you don't have lemons on hand.
Draining your ricotta can take up to 30 minutes to remove all the excess water.
Top the sunken part of the ricotta cheesecake with your favorite jam or fresh berries and dust with powdered sugar.