Preheat oven to 175 degrees C. Line an 20cm square cake pan with baking paper.
Beat pumpkin puree, sugar, oil, eggs, spice and vanilla extract together in a bowl.
Sift flour, bi carb, baking powder and salt into a bowl. Add to the pumpkin mixture; stir until just combined. Pour into prepared pan; smooth top with a spatula.
Bake until a skewer inserted into the centre comes out clean, 35 to 40 minutes.
Combine caramel sauce and half the bourbon in a saucepan over low heat; warm through, about 2 minutes. Poke holes evenly over the surface of the cake using a chopstick. Reserve 1 teaspoon of the caramel-bourbon mixture; pour remaining mixture over the cake. Place on cooling rack. Cool.
Beat cream and remaining bourbon in a bowl using an electric mixer until soft peaks form. Spoon whipped cream on cake; scatter pecans and drizzle reserved caramel sauce on top.