Grease the loaf pan (refer notes) with butter or line with baking paper and keep aside.
In a large bowl, add the self raising flour, whole wheat flour, salt and baking soda.
Into a blender, add the avocado, banana, sugar, milk, yoghurt, oil and lemon juice. Blend till smooth and pour into the dry ingredients. Whisk till incorporated.
Pour into the greased loaf pan and bake for 1 hour 20 minutes or till done. Turn the pan around halfway through to ensure even cooking. Since oven temperatures can vary, check after 45 minutes, and thereafter every 5-10 minutes. To confirm if the bread has cooked through, insert a skewer in the middle of the loaf, the bread is cooked if the skewer comes out clean.
Cool for 30 minutes before slicing.
If you do not have self-raising flour, replace with all purpose flour but add 2 tsp baking powder to the dry ingredients.
If you have a small loaf pan, then use two and fill up only till the halfway mark as the batter does rise up.