Preheat oven to 350°. Grease and flour a 9 x 13 pan.
Place 1 1/2 tablespoons lemon juice in a measuring cup. Top to 1 1/2 cups with milk. Set aside.
Mix together mashed banana with 1 tablespoon lemon juice, set aside.
Beat together butter, brown and white sugar until combined. Add in eggs one at a time and vanilla. Mix on high until light and fluffy (almost the texture of frosting).
Combine flour, baking soda and salt in a medium bowl. Alternate adding flour mixture and milk to egg mixture stirring just until combined. (Do not overmix). Fold in bananas. Pour into prepared pan.
Put into the oven and reduce heat to 300 degrees. Bake 60 – 70 minutes (see note below) or just until toothpick inserted in center comes out clean (do not over bake).
Remove from oven and place in the freezer for 45 minutes to make the cake extra moist. Cool completely before frosting.
Cream together butter & cream cheese until fluffy. Add in lemon zest and juice.
Add powdered sugar a little at a time until you reach desired consistency. Spread over cooled cake.
The cooking time on this cake can vary! Mine takes about 60 minutes. Check your cake at 55 minutes, if it isn’t ready, continue cooking until a toothpick comes out clean (this can be up to an additional 20-30 minutes depending on your oven).