Pre-heat the oven to 180 degrees Celsius and grease a loaf pan with butter and line with parchment paper.
Add the peeled banana to a large bowl. Using an immersion blender, puree the banana until smooth. Whisk in the eggs one by one, followed by the melted butter and the lemon juice.
In a separate bowl, whisk together the baking soda, salt, sugar and flour. Add the dry ingredients to the wet ingredients and stir to combine.
Divide the batter in two. Add the cacao and espresso to one half of the batter and whisk until just combined.
Fill the batter into the prepared loaf pan alternating between the plain batter and the cacao batter. Once finished, use a fork to gently swirl the two batters together – this is what will give the finished cake a marbled pattern.
Bake the loaf for about 1h or until a wooden skewer inserted into the centre of the loaf comes out clean.
Hi, my name is Sophia and I have a passion (ok, maybe it is veering towards an obsession) for food and all things food-related: I read cookbooks for entertainment and sightseeing for me invariably includes walking up and down foreign supermarket aisles. I love to cook and bake but definitely play around more with sweet ingredients.
Current obsessions include all things fennel (I hope there is no cure), substituting butter in recipes with browned butter, baking with olive oil, toasted rice ice cream, seeing whether there is anything that could be ruined by adding a few flakes of sea salt and, most recently, trying to bridge the gap between German, English and Italian Christmas baking – would it be wrong to make a minced meat filled Crostata?