Simmer strawberries: Puree fresh strawberries and cook in a saucepan over medium heat until reduced to 1 cup. Cool completely.
Bake cake base: Mix flour, cocoa, oil, buttermilk, vinegar, 1 egg, red dye, and 1/2 cup sugar. Bake at 350°F for 15 mins in a greased springform pan.
Make filling: Lower oven to 325°F. Beat cream cheese and remaining sugar until smooth. Add reduced strawberry puree, sour cream, and remaining 3 eggs one by one.
Assemble and bake: Pour filling over the crust. Place pan in a water bath and bake for 55-65 mins until center jiggles slightly.
Chill: Turn off oven, crack door, and let cool 1 hour. Refrigerate 6+ hours before serving.
