Method

• Make the dough: In a large bowl, whisk together the flour, baking powder, and salt. Cut in the butter until the mixture resembles coarse crumbs. Stir in the sugar, egg, and milk until just combined. 
  
  
• Make the filling: In a small bowl, combine the guava puree, sugar, lemon juice, and cinnamon.
  
  
• Assemble the duff: Roll out the dough on a lightly floured surface to a 12-inch circle. Spread the guava filling evenly over the dough. Roll up the dough tightly.
  
  
• Cut into slices: Cut the rolled dough into 8-10 slices.
  
  
• Bake: Bake in a preheated oven at 375°F (190°C) for 30-35 minutes, or until golden brown.
  
  
• Serve: Serve warm with vanilla sauce or whipped cream.