Finely dice the onions, celery, and carrots as small as you possibly can. This creates a smooth base for your ragù.
Heat a generous drizzle of olive oil in a large, heavy-bottomed pot or Dutch oven over medium heat.
Add the diced vegetables to the pot and cook gently until they are softened and fragrant. This should take about 10-15 minutes; don't rush this step, as it builds the flavor foundation.