Tomato Caramelized Onion Conserves - cooking recipe

Ingredients

2 tablespoons butter, unsalted
2 tablespoons olive oil
2 1/2 lbs sweet onions, quartered then sliced thinly
3 garlic cloves, sliced thinly
2 teaspoons salt
1 teaspoon packed light brown sugar
10 cups diced tomatoes
3/4 cup honey
1 teaspoon diced fresh rosemary
1 teaspoon fresh thyme leave
1 1/2 teaspoons black pepper
1/4 teaspoon red pepper flakes
1/3 cup white balsamic vinegar

Preparation

In a large pan heat the butter and oil. Add onion, garlic, salt and sugar cook over medium-low heat till golden brown about 20-30 minutes.
Add tomatoes bring to a boil then reduce heat to simmer for 15 minutes. Softening the tomatoes and reduce the liquid. Add remaining ingredients bring back up to a boil then remove from heat.
Ladle into sterilized jars leaving 1/4 inch head space. Wipe rims and adjust lids. Process the jars for 5 minutes.
Remove from canner and let cool.