In a large, heavy pot over medium heat, heat butter. Add onion, carrots, and celery and cook until soft, about 7 minutes. Season with salt and pepper, then stir in garlic and tomato paste. Cook until garlic is fragrant and tomato paste coats vegetables, about 2 minutes. Sprinkle over flour and cook, 1 minute more.
Pour in seafood stock and wine, then stir in bay leaf and thyme. Reduce heat and let simmer until liquid is reduced and flavors meld, stirring occasionally, 30 minutes.