Preheat your oven to 350° Fahrenheit
Cream together the butter and sugar
Add eggs one at a time, mixing until smooth
In a medium bowl whisk together the flour, baking powder, and salt
Whisk your milk, yogurt, and extract in a separate jug
Add ½ of the dry mixture to the butter mixture and mix to combine
Add the rest of the dry mixture and mix thoroughly
Thoroughly grease an 8x8 pan with nonstick cooking spray and line with parchment paper
Place the rhubarb pieces along the bottom of the pan in an even layer
In a medium sauce pan add the sugar and water
Turn the stove on medium heat, swirling the pan constantly, until the mixture is boiling and reaches a medium shade of amber
Pour the bubbling sugar mixture over the rhubarb
Add the cake batter on top of the rhubarb and caramel and smooth into an even layer with an offset spatula
Bake the upside down cake for 35-40 minutes or until the top is golden brown and springs back to the touch
Run an offset spatula along the sides of the pan to release the edges
Let the cake cool for 5 minutes
Invert the cake onto a serving plate
Slice and enjoy
