Preheat the oven to 350˚F and grease and lightly flour a 9x5" loaf pan.
In a large bowl, use a fork to mash the bananas until they are in a rough puree.
Add the remaining wet ingredients to banana puree: olive oil, eggs, sugar, and vanilla, and mix well. Set aside for a few minutes.
In another smaller bowl, combine the dry ingredients: almond flour, buckwheat flour, baking soda, salt and spices. Whisk until everything is mixed together. Please note that almond flour does tend to clump together. To avoid lumps of almond flour in the final batter, I use my fingers to sift through the dry ingredients and break up and lumps. Alternatively, you can use a sifter when measuring the almond flour.
Pour the dry ingredients into the wet ingredients bowl all at once, and fold or gently mix until everything is fully combined.
Using a rubber spatula, pour the batter into the pan.
Bake the banana bread at 350˚F for 1 hour and 15 minutes, or until an inserted toothpick comes out clean. Be sure to turn the banana bread in the oven halfway through baking so that it bakes evenly on all sides.
Allow the banana bread to cool in the pan for about 20 minutes. When the pan is cool enough to handle, use a butter knife to cut around the edges, against the inside of the pan in case any parts of the banana bread have stuck. This helps it come out of the pan more easily.
Tip the loaf pan upside down and gently tap each edge of the pan against the countertop to get the banana bread out. It should come out fairly easily.
Allow the banana bread to cool another 15 minutes before cutting into slices.