Halve, core, peel and dice the pumpkin. Cook in a little water until soft and puree, preheat the oven to 180 degrees.
Mix the softened butter with the sugar until creamy, for about 5 minutes and then stir in the eggs until everything is well combined.
Mix the pumpkin puree, orange zest and orange juice in a bowl. Mix the flour, baking soda, baking powder and spices as well and stir alternately with the pumpkin mixture into the butter mixture. If you like, stir in the walnuts.
Grease a 21 × 11 loaf pan and fill it with the batter. Bake in the preheated oven for 55 - 60 minutes until golden brown. You can also do a chopstick test, as each oven heats differently.
Let the cake stand in the tin for about 5 minutes, remove and let cool on a wire rack.