Pat the pork roast dry with paper towels, then season generously with salt, pepper, and cinnamon on all sides.
Heat olive oil in a large skillet over medium-high heat until shimmering, then carefully place the pork in the pan.
Sear the pork for about 4-5 minutes per side until deeply golden brown and caramelized, then transfer it to a slow cooker or Dutch oven.
Add sliced onions and minced garlic to the skillet, cooking for 2-3 minutes until fragrant and slightly softened, scraping up browned bits from the bottom each time.
Pour the onions and garlic along with their fragrant juices over the seared pork.
Deglaze the skillet with the apple cider, scraping any remaining bits, then pour this mixture over the pork and onions in the slow cooker or Dutch oven.
Cover tightly and cook on low for 6-8 hours, until the pork is fork-tender and easily pulls apart.
Once cooked, remove the pork and set aside. Turn the heat to high and simmer the cider mixture uncovered for about 15-20 minutes, stirring occasionally, until it reduces to a glossy glaze that coats the pork.
Shred the pork with two forks until it has a tender, pull-apart texture, then return it to the glazed sauce, tossing gently to coat evenly.
Taste the sauce and adjust seasoning with salt and pepper as needed, then serve the pork hot, garnished with fresh herbs if desired.
