1. Position the rack in the middle of the oven and crank the heat to 350°F. Grease a 10-inch springform pan with butter, line the bottom with parchment paper, and grease the paper. Coat the pan with flour and tap out the excess.

2. Buzz the almonds and 1/4 cup of the sugar in a food processor until the consistency of fine cornmeal. Really lean on that button to make sure the almonds are as finely chopped as possible. Add the butter and pulse to combine. Set aside.

3. In the bowl of a stand mixer fitted with the paddle attachment, or with a handheld mixer in a big bowl, beat 3/4 cup plus 2 tablespoons of the sugar and the yolks on medium-high until very light and fluffy, about 7 minutes. Add the zest, salt, and cinnamon and mix until incorporated. Whirl in the almond mixture and vanilla.

4. In an impeccably clean bowl, whisk the egg whites until foamy then slowly whisk in the remaining 2 tablespoons of sugar until the whites form soft, luscious peaks. Plop a spatulaful into the almond mixture and stir to lighten. Carefully fold in the remainder of the whites until no streaks show. Spoon the batter into the pan and smooth the top.

5. Bake until the cake is golden brown and begins to pull away from the sides of the pan, about 45 minutes. Transfer to a rack and let rest for 5 minutes before releasing the cake from the pan. Cool completely before serving. The middle will collapse a bit; that is as it should be.