Preheat your oven to 350°F and grease two pans - I used 8" round pans, and if you use different sizes, your cooking times may vary.

In a small mixing bowl, whisk or sift together the flour, salt, cinnamon, and baking soda.  In another bowl, mash the bananas until they are creamy; don't worry if they have some lumps.  Add the lemon and Greek yogurt to the bananas and continue to mash everything together until well combined.

In a large mixing bowl, gradually add the butter to the sugar and cream together thoroughly.  Continue to beat the butter and sugar, while adding the eggs, one at a time, and beating well after each one, then mix in the vanilla.

Begin adding your dry ingredients and the banana and yogurt mixture to the large mixing bowl. Add a small amount of the dry ingredients to the egg/sugar/butter bowl, then add some banana mixture, alternating and beating continuously to combine ingredients between additions.

Evenly distribute batter between the two pans, and cook on the center rack of your oven for 29-32 minutes, or until a toothpick inserted into the center of the cake comes out clean when removed.  My two cakes took ~31 minutes, but cooking time will vary by oven and pan size.

Note: be sure to grease your pans very well or use parchment paper, because these cakes seem to like to stick to the bottoms.

Mash your banana, cinnamon, lemon juice, and vanilla until combined.

In a large mixing bowl, beat the butter until fluffy.  Gradually add the crushed banana to the butter, beating until the mixture is creamy.

Continue to beat the mixture, adding the sugar ½ cup at a time, until 3 cups has been incorporated and the frosting is fluffy and stiff.  Slowly bat in the remaining powdered sugar, in smaller amounts, until the frosting is to your liking.  

Note:  This is more of a "spreading" frosting than a "piping" frosting.  It's quite stiff, especially once it's set a bit.  If it's too difficult to spread by the time you're ready to assemble the layers, microwave it at 10-second intervals until it softens, and stir well before using.

Once your cakes have completely cooled, spread half of the frosting on the top of the first layer of cake.  Set the second layer on top of the first, and spread the remaining frosting on the top of the cake.