For whipped cream, sprinkle unflavored gelatin over cold water. Let stand until softened, about 2-3 minutes. Heat in microwave 10-15 seconds; stir until dissolved and liquid; repeat if needed. In large bowl, whip cream and confectioners' sugar to soft peaks. Add dissolved gelatin and strawberry puree; whip until well combined. Refrigerate 2-3 hours, or until gelatin has set and cream is spreadable.
Preheat oven to 325°F. Prepare pans with vegetable pan spray.
In large bowl, stir together flour, cocoa powder, baking powder, baking soda and salt. In large bowl, beat butter and sugar with electric mixer until light and fluffy. Add eggs one at a time, mixing well after each. Add vanilla; mix well. Add flour mixture alternately with buttermilk, beating until just combined. Divide evenly into prepared pans.
Bake 18-21 minutes, rotating pans half way between baking. Cakes are done when toothpick inserted in center comes out clean. Cool 5 minutes on cooling grid; remove from pans and cool completely.