Beat cream cheese until fluffy. Add sugar, salt, egg, lemon juice and vanilla; mix until smooth. Pour into unbaked pie crust, one that you have made from your own favorite recipe or a pre-made frozen (thawed). Bake in a preheated 350 F oven for 20 minutes. Remove from oven, and now preheat oven to 400 F.....while preheating spread blackberry filling over cheese mixture...return to oven and bake another 20 minutes until crust is golden brown. Cool and refrigerate. *IMPORTANT...when returning pie to the oven for the second time be sure to use a pie crust (edge) guard OR tin foil to cover the edges of the crust..at this high heat it could end up burning the edges. Remove from oven and cool on rack completely and then keep refrigerated.