Adjust the oven rack to the middle position, pre-heat the oven to 375ºF (190ºC) and line a 2lb/900g (9x5-inch/23x13cm) loaf baking tin with parchment/baking paper.
In a large bowl, combine the mashed bananas with lemon juice, and then add the melted vegan butter, light brown sugar, vegan yoghurt and vanilla. Whisk everything together until well combined.
In a separate bowl, whisk together the plain gluten free flour blend, baking powder, baking soda, xanthan gum, salt, cinnamon and nutmeg.
Add the dry ingredients to the wet, and whisk well until you get a smooth batter with no flour clumps (though you might have a few small banana pieces in there, depending on how well you mashed them).
Fold in the chopped toasted pecans until they're evenly distributed in the batter.
Tip: You can reserve some of the chopped pecans for scattering on top of the batter before baking, if you wish.
Transfer the batter into the prepared loaf tin and smooth out the top. If you've set aside any chopped pecans, scatter them over the top.
Bake in the pre-heated oven at 375ºF (190ºC) for about 1 hour - 1 hour 10 minutes, or until well risen, golden brown on top and an inserted toothpick/skewer/cake tester comes out clean or with a few moist crumbs attached.
If the banana bread starts browning too quickly, cover it with a sheet of aluminium foil (shiny side up) and continue baking until done. It's best to cover it with aluminium foil when it starts becoming a deep golden colour.
Once baked, allow it to cool in the loaf tin for about 10 minutes, then transfer it out of the tin and onto a wire rack to cool.
The banana bread is best served warm or cooled completely to room temperature.