For the Filling: In a bowl, beat cream cheese and sugar on medium speed until smooth. Beat in egg until mixture is smooth. Set aside.
Combine flour and sugar; cut in butter until pea-sized lumps remain; mixture will be dry and crumbly. Reserve 3/4 cup for topping. To the remaining mixture, add baking powder, baking soda, and salt. In a separate bowl, gently whisk together the egg, sour cream and vanilla until combined; fold/stir sour cream mixture into flour mixture
– Spread cake batter evenly into bottom of greased springform pan. Spread custard layer over crust, leaving a 1/2-in. border around edge of pan. Spoon strawberry sauce evenly over the top. Sprinkle with reserved 3/4 cup of crumb mixture on top.