For the cake
1½ cups (12 oz.) bananas, mashed, ripe
2 teaspoons lemon juice
3 cups (12¾ oz.) flour
1½ teaspoons baking soda
¼ teaspoon salt
¾ cup (6 oz.) butter, softened
1½ cups (10½ oz.) granulated sugar
3 large eggs
2 teaspoons vanilla
1½ cups (12 oz.) buttermilk

For the frosting
8 ounces cream cheese, room temperature
¼ cup unsalted butter, room temperature
½ cup (40g) cocoa powder
2 cups sifted powdered sugar (You can increase this amount if you would like it to be thicker, for piping)

For the assembly
One banana, sliced (optional)