Heat the oven to 325 °F and place a rack in the middle, then stir the almond flour, powdered sweetener, and cinnamon together before mixing in the melted butter. The crust mixture should feel evenly moistened and sandy, with no dry pockets hiding in the bowl.

Press the crust mixture into a 10-inch springform pan, bringing it about halfway up the sides with your fingers and flattening the bottom with a flat-bottomed cup, then bake for 5 to 8 minutes. It is ready when the crust smells lightly nutty and looks just a touch deeper in color.

Set the crust aside and beat the room temperature cream cheese in a large bowl with a hand mixer until it turns light and fluffy, or use the paddle on a stand mixer if that is what you have. At this stage, the cream cheese should look completely smooth, like a thick Greek yogurt, with no visible lumps.

Add the powdered sweetener gradually, about one-third at a time, beating after each addition until the mixture stays smooth. Scrape the bowl as needed so you do not end up with streaks of unmixed cream cheese later.

Mix in the room temperature eggs one at a time, blending each one in before adding the next. Keep the batter smooth but do not whip it aggressively, because too much air can make the cheesecake rise and then crack.

Add the vanilla extract and room temperature sour cream, then mix only until the filling is combined. The batter should look glossy, thick, and uniform, not foamy.

Pour the filling into the baked crust, smooth the top, and bake, checking after 50 minutes. The cheesecake is done when the surface is no longer glossy, the edges are set, and the center still has a slight jiggle.

Turn the oven off, crack the door, and leave the cheesecake inside for 30 minutes, then remove it and run a sharp paring knife between the cake and pan without unlocking the springform. This gentle cooling step helps the cheesecake settle instead of shrinking too fast and splitting on top.

Let the cheesecake stand on the counter for 1 hour, then cover loosely with plastic wrap or aluminum foil and refrigerate for at least 8 hours. It might feel underdone at first, but trust the process because the center firms up fully as it chills.

Remove the springform sides, decorate the top if you like, and slice into 12 pieces to serve. A clean, cold cheesecake will cut with neat edges and a dense, creamy center.