Bring a large pot of water to a boil and add 1 tablespoons kosher salt. Cook pasta according to package directions.
Place onion in a large bowl. When pasta is done, drain it well and add it to the bowl. Add garlic powder and apple cider vinegar and stir. Let sit 10 minutes.
In a medium bowl, whisk together mayonnaise, milk, and sugar.
Set aside about 1/2 a cup and add the rest to the macaroni along with carrots. Stir to combine. Season to taste with salt and pepper.
Cover and refrigerate both the bowl of macaroni salad and the reserved 1/2 a cup of mayonnaise mixture. Refrigerate for at least 2 hours before serving. Stir in the reserved mayonnaise mixture just before serving.
Notes
Be sure not to overcook your pasta or it will have a mushy texture.If you to dress it up some, add diced ham or chopped pineapple.