How to Make It
Heat oil in a large Dutch oven over medium heat. Add onion to pan; cook 4 minutes, stirring frequently. Add sugar and next 7 ingredients (through fennel seeds); cook 1 minute, stirring constantly. Stir in vinegar; cook 30 seconds. Add broth and tomatoes; bring to a simmer. Cook over low heat for 55 minutes or until sauce thickens, stirring occasionally.
To store in the freezer: Ladle room-temperature or chilled sauce into plastic containers or zip-top plastic bags. Seal and freeze for up to four months. Consider freezing the sauce in one-cup increments (two servings' worth). That way, you can pull out exactly as much as you want for future meals.
To thaw sauce: Try one of three methods.
Thaw in the refrigerator overnight.
Place frozen blocks in a saucepan. Cover and bring to a low simmer over medium heat, stirring occasionally.
Place frozen blocks in a microwave-safe bowl. Cover and microwave at HIGH one minute at a time, stirring after each increment until thawed.
To boost taste: Long stints in the freezer can dull the taste of tomatoes. To perk up thawed sauce, add one-half teaspoon finely grated lemon rind or one teaspoon balsamic vinegar while reheating.