Preheat your oven to 350°F (177°C). Grease and flour a 9x13-inch pan.
Mix mashed bananas and lemon juice together in a bowl and set aside.
In a separate bowl, whisk together flour, baking soda, and salt.
Using a mixer, cream butter and sugar together until light and fluffy.
Beat in the eggs, one at a time, then stir in the vanilla.
Mix in the banana mixture. Alternate adding flour mixture and milk, beginning and ending with flour.
Pour the batter into the prepared pan and bake for 60–70 minutes, or until a toothpick comes out clean.
Let the cake cool completely before frosting.
To make the frosting: beat cream cheese and butter until smooth. Add powdered sugar gradually, then stir in vanilla.
Spread the frosting over the cooled cake and refrigerate before serving for best texture.