In a large heavy-bottomed pot, melt 1/2 cup of unsalted butter over medium-low heat. Gradually whisk in 1/2 cup of all-purpose flour, stirring constantly for about 10-30 minutes until the mixture turns a deep caramel color.

Add 1 chopped yellow onion, 1 chopped green bell pepper, and 2 finely sliced celery stalks to the roux. Cook for about 5-7 minutes, until the vegetables have softened.

Stir in 12 oz of sliced Andouille sausage and 2 finely chopped garlic cloves. Cook for about 2 minutes, then add 1 tablespoon of Cajun seasoning, kosher salt, and black pepper to taste.

Pour in 4 cups of low-sodium chicken broth and add a 15-oz can of fire-roasted diced tomatoes along with 1 bay leaf, bringing the mixture to a boil.

Lower the heat and let your gumbo simmer on low for about 1 hour, stirring occasionally.

With about 6 minutes left in the cooking time, add 1 lb of peeled and deveined medium shrimp. Stir gently until the shrimp turn pink.

Ladle the gumbo over a bed of cooked white rice and garnish with reserved scallions.