Finely chop the onion, pepper, and celery into roughly even sized pieces. Finely chop or crush the garlic. Melt the butter in a medium skillet and saute the onion, celery and pepper until soft, around 5 minutes. Add the garlic towards the end and cook a minute longer.
½ onion, ½ green pepper, 1 stick celery, 2 Tablespoons butter, 2 cloves garlic
Add the tomato paste, salt, sugar, oregano, thyme, black pepper, and cayenne and mix through. Cook a minute then add tomatoes, bay leaf, Worcestershire sauce, and stock. Mix through, bring to a simmer and leave to reduce a little, around 15-20 minutes. Reduce heat as needed so that it simmers rather than boils.
2 Tablespoons tomato paste, ¼ teaspoon salt, ¼ teaspoon sugar, ⅛ teaspoon oregano, ⅛ teaspoon thyme, ⅛ teaspoon black pepper, 1 pinch cayenne pepper, 1 cup chopped tomatoes, 1 teaspoon Worcestershire sauce, ½ cup shrimp stock, 1 bay leaf