Place the butter in a bowl, whisk in the sugar and salt. Add the eggs and continue to beat until the mixture becomes lighter in colour. Stir in the carrots and milk. Mix the flour and baking powder, stir into the mixture and transfer to the prepared tin.
For approx. 20 mins. in the centre of an oven preheated to 180°C. Remove from the oven, allow to cool a little for about 10 mins., remove from the tin, leave to cool completely on a rack.
Caramel & vanilla frosting
Boil the sugar and water in a wide pan without stirring. Reduce the heat and simmer, shaking the pan occasionally until a light brown caramel has formed. Remove the pan from the heat. Add 50g of the butter to the caramel, allow to melt, stir well and leave to cool for approx. 15 mins. Combine the remaining butter with the vanilla and stir into the caramel with the cream cheese. Transfer the frosting to a piping bag with a serrated nozzle (approx. 10 mm in diameter) and pipe onto the cupcakes.
Sprinkle the pumpkin seeds over the cupcakes.