Step 1: Prepare the Red Velvet Cake Layer

1. Preheat oven to 350°F (175°C). Grease a 9-inch springform pan and line the bottom with parchment paper.
2. In a large bowl, whisk together flour, sugar, cocoa powder, baking soda, and salt.
3. In another bowl, mix buttermilk, oil, egg, vanilla extract, vinegar, and red food coloring.
4. Gradually add wet ingredients to dry ingredients, mixing until just combined.
5. Pour the batter into the prepared pan and bake for 15-18 minutes or until a toothpick comes out clean.
6. Let the cake cool in the pan.

Step 2: Prepare the Cheesecake Layer

1. Lower oven temperature to 325°F (163°C).
2. In a large bowl, beat softened cream cheese and sugar until smooth.
3. Add eggs one at a time, mixing on low speed until incorporated.
4. Mix in vanilla extract and sour cream until smooth.
5. Pour cheesecake batter over the cooled red velvet cake layer.

Step 3: Bake the Cheesecake

1. Place a baking sheet with hot water on the oven’s lower rack to prevent cracking.
2. Bake cheesecake for 40-45 minutes, until edges are set and the center slightly jiggles.
3. Turn off the oven, leave the door slightly open, and let the cheesecake cool for 30 minutes.
4. Refrigerate for at least 6 hours or overnight.

Step 4: Prepare the Strawberry Topping

1. In a saucepan over medium heat, combine chopped strawberries, sugar, and lemon juice. Stir occasionally.
2. Mix cornstarch with water and stir it into the strawberry mixture.
3. Cook for another 2-3 minutes until thickened, then let it cool.

Step 5: Assemble and Serve

1. Spread cooled strawberry topping over the chilled cheesecake.
2. Decorate with whipped cream and fresh strawberries if desired.
3. Remove from the springform pan, slice with a warm knife, and serve chilled.