In a medium to large bowl mix together 330 grams water and sourdough starter until combined.

Add flour and mix together until a shaggy dough forms. Cover bowl with Saran Wrap and let rest for 1 hour.

Mix together salt in 30 grams of water until dissolved. Work this into the dough evenly. Cover bowl with Saran Wrap and let rest for 1 hour.

stretch and fold the dough 3 time, 30 minutes apart, covering with Saran Wrap in between. On the second stretch and fold set, add in your shredded cheese and caramelized onions. These will incorporate as you stretch and fold.

Leave in covered bowl at room temperature for 2-3 hours for first rise.

on a floured surface, shape the dough into a rough ball. Flour the top, and put into your proofing basket face down. Cover with Saran Wrap and chill overnight.

The next morning, preheat your oven and Dutch oven to 500 degrees for 30 minutes. Take your dough out and score it on a piece of parchment paper. Use parchment to lift the dough into the Dutch oven. Cover and bake at 450 for 30 minutes. Take lid off and bake for 15-25 more minutes, depending on oven.

Wait two hours before cutting open.