Grease a 8”x8” square cake pan and line it with parchment paper
Preheat toaster oven 350 F
In #1 bowl, unpeel and mash bananas with a potato masher or fork. Some large chunks are ok! Set aside
In #2 bowl (your largest bowl), cream butter, vanilla and sugars until light and fluffy with hand mixer at least 7 mins. The mixture should not be clumping to the mixer attachment and should become paler in color when mixed thoroughly. This ensures enough air for a light and fluffy cake
Add in eggs one at a time to #2 bowl and mix thoroughly. About 5 mins
In #3 bowl, mix flour, kosher salt and baking soda with a hand whisk
Add #1 bowl of mashed banana to #2 butter/sugar bowl. Mix wet batter by hand gently with a spatula
Pour in #3 bowl dry flour mixture to #2 wet batter. Fold super gently by hand with the spatula no more than 1 min until flour is JUST mixed. Never overmix! Overmixing forms more gluten bonds resulting in a tougher cake!
Pour batter into prepared cake pan
Put cake into oven for 35-40 mins until tooth pick pierced in centre comes out clean (a few crumbs should be attached)
Cool and cut into 2 inch squares