Combine the baking powder, cinnamon, ginger, flour and ¼ tsp fine sea salt in a bowl. Fold the dry ingredients into the wet, then add the mashed banana. Scrape into the tin and bake for 45 mins-1 hr until dark golden and a skewer inserted into the middle comes out clean. If it browns too quickly, turn the oven down to 160C/140C fan/gas 3 towards the end of the bake time. Leave to cool in the tin for 10 mins, then put on a wire rack to cool fully. Best made a day in advance. Store in an airtight container.
