In a bowl, combine graham cracker crumbs and butter; stir until crumbs are evenly moist. Press into a 9” springform pan. Place pan on a baking sheet and bake for 10 minutes.
Remove from oven and cool to room temperature.
To make the filling:
Reduce oven temperature to 325°F.
In a large bowl using an electric mixer, beat cream cheese, Splenda Sweetener, and flour until smooth. Add vanilla extract and mix until smooth.
Add eggs one at a time, mixing well after each addition. Add milk and mix until well blended.
Measure ½ cup of the cheesecake batter into a small bowl; add dulce de leche and stir until well combined.
Pour plain batter over crust. Spoon dulce de leche batter in dollops over the cheesecake batter and gently swirl with the tip of knife.
Bake 45–55 minutes or until center is almost set. Remove from oven and gently run a metal spatula around rim of pan to loosen cheesecake (this helps prevent cracking).
Let cool 20–25 minutes before covering and placing in the refrigerator. Refrigerate 4–6 hours or overnight.