Cream the butter and cream cheese together until fluffy.
Add the zest, juice, salt, and slowly combine the powdered sugar. Beat it on medium speed for a couple of minutes until its light and fluffy. (If your buttercream is too soft you can either add a bit more cream cheese or refrigerate it).
To frost the cakes, add half the buttercream to one layer, spread out evenly, then top with the other cake layer.
Spread remaining frosting on the top layer.
Garnish with fresh berries and slices of Meyer lemons. Chill any leftovers.