Arrange your macaron shells for piping. You'll want to pair up matching sizes of macaron shells so they can easily be sandwiched together to give you a uniform macaron.
Fit a piping bag with a star nozzle for a bit of design to the buttercream, or you can use a round tip for easy piping. The tip should be at least 1 cm in diameter.
Add salted caramel buttercream to the piping bag.
Pipe a ring of buttercream on the outer edge of the macaron. This will help keep the salted caramel sauce tucked inside the macaron.
Using a small spoon, pour a spoonful of caramel sauce in the center of the macaron.
Close the macaron by adding a plain macaron shell on top.
Store macarons in the fridge for up to 3 days, and up to 1 month in the freezer.