Preheat the Oven. Preheat your oven to 325°F. Position the rack in the center.
Prepare the Springform Pan. Grease a 9-inch springform pan with butter or cooking spray.
Make the Gluten-Free Crust. In a mixing bowl, combine the gluten-free graham cracker crumbs, sugar, melted butter, and ground cinnamon (if desired). Stir until all ingredients are well combined and the mixture has a consistency like wet sand. Press the crumb mixture firmly into the bottom of the prepared springform pan, ensuring it's evenly distributed. Place the pan in the refrigerator to set while you prepare the filling.
Prepare the Cheesecake Filling. In a large mixing bowl, beat the softened cream cheese until smooth and creamy. Add the granulated sugar and vanilla extract, then continue to beat until the mixture is well combined. Add the eggs one at a time, mixing well after each addition. Incorporate the sour cream, gluten-free all-purpose flour, and milk. Mix until the filling is silky and without lumps.
Assemble and Bake. Pour the cheesecake filling onto the chilled crust in the springform pan. Tap the pan gently on the countertop to release any air bubbles. Place the pan on a baking sheet to catch any potential drips. Bake the cheesecake in the preheated oven for about 50-60 minutes. The edges should be set, but the center might still jiggle slightly when the pan is gently shaken.
Allow to Cool. Turn off the oven, crack the oven door open, and allow the cheesecake to cool inside the oven for about an hour. This gradual cooling helps prevent cracks. Remove the cheesecake from the oven and refrigerate it for at least 4 hours or overnight to ensure it's fully set.
Serve and Enjoy. Carefully remove the cheesecake from the springform pan and place it on a serving platter. Slice and serve your gluten-free cheesecake plain or with your favorite toppings, such as fresh berries, chocolate sauce, or whipped cream.