Scrub the celery, carrots and onions.
Chop onions into 1/2-inch cubes, celery and carrots into 1/4-inch cubes.
Heat pan on HIGH. Drizzle 1 tsp extra virgin olive oil to coat the pan.
Add onions. Keep them moving in the pan.
Once the onions become translucent, add carrots and celery.
Sweat the vegetables by letting the vegetables cook uncovered so the moisture in the pan can evaporate. Stir occasionally.