Step 1

Cook onions over medium heat in butter until onions are soft and translucent.

Step 2

Add tomatoes with their juices.

Step 3

Add remaining ingredients and simmer for 30 minutes.

Step 4

Remove bay leaf and puree with an immersion blender or transfer sauce to a blender or food processor.

Step 5

Store in refrigerator for up to 10 days or freeze in freezer safe containers.