Line a 12-section bun tray with paper cake cases. Put the butter, sugar, eggs, flour, baking powder and vanilla extract in a bowl and beat with a hand-held electric whisk for about a minute until light and creamy.
Stir in three-quarters of the pecan nuts and then divide the cake mixture between the paper cases.
Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 20 minutes or until risen and just firm to the touch. Transfer to a wire rack.
Tip the caramel sauce into a small saucepan and stir gently over a medium heat until melted but not boiling. Drizzle the sauce over the cakes while still warm and scatter with the remaining pecan nuts. You may want to take the cakes out of their cases to serve.