**Prepare the Red Velvet Cake Layer:**
- Preheat your oven to 350°F (175°C). Grease and line the bottom of a 9-inch springform pan.
- In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt.
- In a large bowl, beat the butter and sugar together until light and fluffy. Add the egg and vanilla extract, mixing well.
- In a small bowl, combine the buttermilk, red food coloring, and vinegar. Add the dry ingredients to the wet mixture in two parts, alternating with the buttermilk mixture. Mix until just combined.
- Pour the batter into the prepared pan and bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean. Let the cake cool completely.
**Prepare the Cheesecake Layer:**
- Reduce the oven temperature to 325°F (160°C).
- In a large bowl, beat the cream cheese and sugar together until smooth. Add the eggs one at a time, beating after each addition. Mix in the vanilla extract and sour cream until fully incorporated.
- Pour the cheesecake batter over the cooled red velvet cake layer in the springform pan. Smooth the top with a spatula.
- Bake for 50-60 minutes, or until the cheesecake is set and the center is slightly jiggly. Turn off the oven and leave the cheesecake inside with the door slightly open for 1 hour.
- Remove the cheesecake from the oven and let it cool to room temperature. Refrigerate for at least 4 hours, preferably overnight.
**Prepare the Strawberry Topping:**
- In a medium saucepan, combine the sliced strawberries, sugar, and lemon juice. Cook over medium heat until the strawberries release their juices and soften, about 5-7 minutes.
- Stir in the cornstarch mixture and cook for an additional 1-2 minutes, until the sauce thickens slightly. Remove from heat and let the sauce cool to room temperature.
**Assemble the Cheesecake:**
- Once the cheesecake is fully chilled, remove it from the springform pan and place it on a serving plate.
- Spoon the strawberry topping over the cheesecake, allowing some to drip down the sides for a beautiful presentation.
- Slice and serve the Strawberry Red Velvet Cheesecake, enjoying the delightful combination of flavors in every bite.