Preheat oven to 350°F. Lightly grease a 10 inch springform baking pan.
In a medium bowl, whisk together the flour, baking powder, cinnamon and salt. Set aside.
In a stand mixer, cream together the butter and sugar for about 5 minutes, or until light and fluffy. Add one egg at a time until well incorporated. Add the vanilla extract. Turn mixer on low and slowly add the flour mixture. Don’t over mix. Fold in the cut rhubarb and transfer the dough to the baking pan. Drizzle on the caramel and swirl in with a knife.
Bake for about 35 minutes or until an inserted toothpick comes out clean. Let cool completely on wire rack before slicing and serving.