Beat the eggs and sugar : I like to use a stand mixer or hand mixer for this, but you can also just use a whisk. You want the eggs and sugar to fluff up bit and be pale in color.
Whisk in the oil : Slowly drizzle in the oil while whisking.
Mix : Time to mix in the smashed banana, sour cream, and vanilla.
Fold : Gently fold in the dry ingredients until there are no flour streaks.
Bake : Pour everything into a oiled and floured (or nonstick) loaf pan and bake until golden and cooked through. Let cool, slice, and enjoy!