Make streusel: Whisk flour, brown sugar, and cinnamon in a bowl. Add almond butter and oil and use a fork to stir and mash them into the dry ingredients until you get large crumbles. You can also use your fingers to pinch the mixture together. Set aside.
Mix wet ingredients: Mash bananas in a large mixing bowl, then whisk in brown sugar, almond butter, soy milk, vanilla extract, lemon juice, and miso or salt.
Fold in dry ingredients: Sift whole wheat flour, baking powder, cinnamon, and nutmeg over the wet ingredients. Fold the dry and wet ingredients together just until there is no dry flour left. Be careful not to overmix.
Rest batter: Cover the bowl and let the batter rest for 20 minutes.
Preheat oven to 350°F/180°C. Line an 8x8-inch pan with parchment paper, leaving excess parchment paper on the sides to make removing the cake easier.
Add baking soda and blueberries after resting: Uncover the mixing bowl and sift baking soda on top. Add blueberries and gently fold into the batter to distribute.
Bake: Transfer batter to your lined baking pan. Sprinkle streusel on top and gently press the streusel into the batter so it sticks. Bake for 40-45 minutes, until a toothpick inserted in the center of the cake comes out clean.
Cool: Place the baking pan on a wire rack to cool for 20 minutes. Carefully remove the coffee cake (grab the sides of the parchment paper) and place directly on the wire rack to finish cooling.
Store: The cake can be stored in an airtight container at room temperature the day it's made. Any leftovers for the next day should be stored in the fridge for up to 5 days.