In a large bowl, whisk together the sifted almond meal and powdered sugar- breaking up any lumps or large bits.
Make a well in the center of the bowl and pour 110 grams of egg whites in. Fold them in gently until the mixture is well combined, thick and paste-like.
Meanwhile, place the other 110 g of egg whites into the bowl of a stand mixer fitted with a whisk attachment. Leave it be while you make the sugar syrup.
In a small saucepan, combine the sugar and water and stir together until dissolved. Clip a candy thermometer to the side of the pan.
When the syrup reaches 225 degrees F- turn the stand mixer on high and start whisking the eggs. You want them to be at soft peak stage, so as soon as they are, turn the speed to low. The egg whites can wait for the syrup- but once the syrup is ready- it cannot wait.
When the syrup hits 239 degrees- carefully pour it into the side of the bowl while the mixer is running. You don't want the syrup to run down the bowl- or it will cool- so aim to pour it right at the spot where the egg whites meet the side of the bowl.
Whip on high for about a minute- and then reduce speed to low and continue beating until the bowl has cooled slightly, and glossy stiff peaks have formed.
Add 1/2 of the meringue to the almond mixture, and gently fold it in until combined and smooth. Gradually add the rest of the meringue until batter is smooth and it almost ribbons off the spoon.
Add gel coloring at this time and fold it in until the batter is smooth and shiny and totally ribbons of the spoon.
Fill piping bags with a round tip and preheat oven to 300F.
Prepare baking sheets with parchment paper. If your oven has a strong fan- you may want to pipe dots of batter onto the corners to stick the parchment down.
Pipe small rounds with the bag perpendicular to the baking sheet.
Let the piped macarons sit out until a trace of a shell is formed- 20-30 minutes will do- maybe less. This helps keep their shape while baking.
Bake for about 15 minutes. To test if done- open the oven and wiggle the top of a shell back and forth. If it's super wiggly they need more time. Perfect macs will be just a little wiggly- but overall firm.
When done, remove parchment from the sheet and let cool for 5 minutes on the counter top. Gently peel parchment paper off and cool completely before filling.
Macarons taste best when "ripened" in the fridge for 24-48 hours, but can last in the fridge air-tight for up to a week or two.
Combine butter & sugar in a stand mixer fitted with the paddle attachment.
Mix on medium-high speed until combined.
Add the strawberry rhubarb compote 1 tablespoon at a time with the mixer on low speed to make sure the filling doesn't get too runny. You want to add as much compote for flavor as possible while still keeping a butter cream consistency.
Scoop the filling into a pastry bag and pipe onto a cooled macaron shell. Place another macaron shell on top and gently press down to sandwich the cookies together.