Preheat the oven to 350°F (180°C).
Butter or spray 12 regular muffin tins or line with paper cups.
Beat ¾ cup sunflower oil with ½ cup brown sugar and ½ cup white sugar for 1 minute in a large bowl.
Add 2 eggs, one by one, beating until fully incorporated but don’t overbeat.
Add 6 tablespoons pumpkin puree, ½ teaspoon vanilla extract and mix well.
Add 6 tablespoons mashed banana and stir to combine.
Sift 2 cups all-purpose flour, 2 teaspoons baking powder, ½ teaspoon baking soda, ½ teaspoon salt and ½ teaspoon pumpkin spice mix. You can use a medium bowl or have them measured and sift them directly over the oil mixture (what I do).
Add the dry ingredients in 2 parts to the pumpkin mixture, integrating well with a spatula. I don't recommend an electric mixer for this part so as not to overmix them.
Fill the paper liners up to ¾ of their capacity. Do not fill more than that so they don’t overflow while baking.
Bake for about 25 minutes or until a cake tester or toothpick comes out dry.
Let cool on a wire rack.
Store covered at room temperature for two days and then refrigerate or freeze, covered or well wrapped. Warm lightly in the oven before eating.