Preheat oven to 250 degrees F or 121 degrees C
Make a marinade by combining your minched garlic, apple cider, apple cider vinegar, worechester sauce, fennel seeds, cayenne pepper and rosemary in a medium sized bowl and mixing well.
Add 1 tablespoon of oil to your dutch oven. On the stove top, cook your apple and onion slices on low until they are very soft and translucent. About six minutes. Remove from dutch oven and place in a bowl while you sear your brisket.
Add the remaining oil into your dutch oven. On medium heat, sear your brisket on both sides (4-6 minutes each side). Make sure fat side is facing up inside of your dutch oven. Turn off heat.
Scoop your apple and onion mixture on top of the brisket.
Add your marinade over the brisket, apples and onion.
Cover and let cook in your oven for 4.5 hours, or until very soft and tender with an internal temperature of ~197-205°F.
Let brisket rest for 10 minutes prior to serving.
