Special equipment: pastry bag with round tip
Whisk together the sugar, flour and salt in a large bowl; set aside.
Beat together the sugar, food coloring, vanilla and egg whites in a separate bowl using a handheld electric mixer until firm. Spread the egg white mixture along the inside of the mixing bowl using a rubber spatula, one third at a time, and fold it over itself. Continue this smoothing and folding motion until the mixture is glossy and drips slowly from the spatula when scooped up.
Prepare a pastry bag with a round tip and fill with the batter.
Trace circles onto parchment paper using a half-dollar-size round cookie cutter, leaving 1 inch around the perimeter of each circle. Flip the parchment paper over to be ink-side down and set into a rimmed baking sheet. Pipe half-dollar-size circles of batter using the marked circles as a guide.
Once all the batter is used, lightly pound the tray onto the countertop to smooth out the top of the batter. Let sit for 30 minutes.
Preheat the oven to 250 degrees F.
For the cream cheese filling: Combine the cream cheese, sugar, butter and vanilla in the bowl of a stand mixer fitted with the whisk attachment or in a large bowl with an electric hand mixer. Beat the mixture on medium speed until smooth and fluffy, 2 to 3 minutes.
Bake the macaroons for 17 to 20 minutes.
To serve, spread the filling between the macaroons and assemble as sandwiches.
To make mini topiary, cover a 7-inch Styrofoam ball with royal icing. Using the royal icing as glue, apply the macaroons to the ball and allow to dry. Once dry, place the finished topiary in a decorative urn.