Balsamic Cherry Tomato Onion Conserve - cooking recipe

Ingredients

2 tablespoons butter
2 tablespoons olive oil
2 lbs sweet onions, quartered and thinly sliced
2 teaspoons sea salt
1 teaspoon sugar
2 pints cherry tomatoes, halved
3/4 cup honey
1/4 cup balsamic vinegar
1/2 teaspoon fresh ground black pepper

Preparation

Heat butter and oil in a large skillet over medium-low heat until butter melts; add onion, salt, and sugar and cook, covered, until onions are tender, about 13 to 15 minutes, stirring occasionally.
Uncover, turn heat up to medium high, and cook and stir until onions are a deep golden brown, about 3 to 5 minutes.
Stir in the cherry tomatoes and honey; bring to a boil, then turn heat down to medium-high and boil until tomatoes are soft, about 5 minutes, stirring frequently.
Remove from heat and stir in balsamic vinegar and season with pepper.
Ladle mixture into hot, sterilized jars, leavin 1/4-inch headspace.
Wipe jar rims and apply lids.
Process jars in a boiling water canner for 5 minutes (begin timing once water returns to a boil); remove jars and cool on wire racks.