Combine the granulated sugar, 1/2 cup water and the cardamom pods in a large skillet. Bring to a simmer over medium heat, stirring occasionally, until the sugar dissolves, about 8 minutes. Add the rhubarb and cook, stirring, until just starting to break down, about 5 minutes. Transfer to a shallow dish and let sit until cooled, about 1 hour. Stir in the strawberries.
Beat the heavy cream with the confectioners' sugar, vanilla and ground cardamom in a large bowl with a mixer until medium peaks form. Slice the angel food cake and top with the strawberry-rhubarb sauce and spiced whipped cream.
Photograph by Ryan Dausch