Preheat oven to 325°F. Line a 9x13 inch baking pan with parchment paper, leaving overhang on all sides for easy removal. Lightly spray parchment with cooking spray. Make sure cream cheese and eggs are at room temperature before starting.

In a medium bowl, mix graham cracker crumbs, ¼ cup sugar, and 1 teaspoon cinnamon. Pour in ½ cup melted butter and stir until mixture resembles wet sand and all crumbs are coated. Press mixture firmly and evenly into bottom of prepared pan using the bottom of a measuring cup to pack it tight.

Bake crust for 10 minutes until lightly golden and fragrant. Remove from oven and let cool slightly while you prepare the filling. Keep oven on at 325°F.

In a large bowl, beat softened cream cheese with ¾ cup sugar using an electric mixer on medium speed for 3-4 minutes until smooth, fluffy, and no lumps remain. Scrape down sides of bowl to ensure everything is incorporated evenly.

Add eggs one at a time, beating on low speed after each addition just until combined. Don't overmix once eggs are added. Mix in vanilla extract and sour cream until just combined. Add flour and mix on low just until incorporated. The filling should be smooth and creamy.

Pour cheesecake filling over the baked crust. Spread evenly to all corners using a spatula. Tap pan gently on counter a few times to release any air bubbles trapped in the batter.

Bake at 325°F for 35-40 minutes. The edges should be set but the center should still jiggle slightly when you gently shake the pan. It will look slightly underdone but will continue to set as it cools. Don't overbake or cheesecake will be dry and cracked.

Turn off oven and crack the door open. Let bars sit in warm oven for 10 minutes to prevent sudden temperature change. Remove from oven and cool at room temperature on a wire rack for 1 hour. Then cover and refrigerate for at least 3 hours or overnight until completely cold and firm.

Once bars are completely cold, use the parchment paper overhang to lift the entire cheesecake out of the pan onto a cutting board. This makes cutting much easier and cleaner.

Brush the top of the cold cheesecake generously with ¼ cup melted butter, making sure to cover every spot. In a small bowl, mix ½ cup sugar with 1 tablespoon cinnamon. Immediately sprinkle cinnamon sugar mixture evenly over the buttered surface. The butter helps it stick.

Using a sharp knife, cut into 16 bars (4 rows by 4 rows). For bite-sized pieces, cut into 24-30 smaller squares. Wipe knife clean between cuts for neat, professional-looking edges. Serve cold or at room temperature.