Preheat your oven to 325F / 160C, then grease and line a 1L loaf tin with baking parchment.
Using an electric whisk, put the butter and sugar into a bowl and cream until pale in colour, and smooth in texture. This should take about five minutes.
Sieve the flour, bicarbonate of soda, baking powder and salt into a separate bowl, and then mix to combine.
Mash your bananas into a third bowl and add your eggs (which should already be whisked together), vanilla extract, sour cream and cider vinegar. Mix together.
Add the wet mixture to your creamed butter and sugar, and whisk again until evenly combined.
Slowly add your bowl of flour in thirds, whisking after each addition and scraping down the sides of your bowl with a spatula as you go. Repeat until you’ve added all the flour, and whisk so everything has been properly incorporated.
You can now add the chopped pecans. Mix with a spoon.
Bake for 1hr 20mins on the middle shelf of your oven. If it still looks a little wet in the middle, add on another 5-10mins. A knife or kebab stick should come out ‘clean’ when inserted into the loaf. Your loaf is fully baked when a skewer inserted into the centre comes out clean or with a few dry crumbs clinging to it.
Leave to cool completely in the tin, before removing the baking parchment and wrapping in foil (or eating immediately).