Wash the asparagus spears and trim. Remove the tough ends.
Place the trimmed asparagus in the slow cooker.
In a small bowl, mix the minced garlic with olive oil. Drizzle the garlic-infused olive oil over the asparagus in the slow cooker, ensuring all spears are coated.
Sprinkle lemon zest, salt, and pepper evenly over the asparagus. Gently toss the asparagus in the slow cooker to coat them evenly with the garlic-infused oil and seasonings. Top with parmesan cheese and dot with butter.
Cover the slow cooker with the lid and cook on low for 1 ½-2 hours or until the asparagus is tender but still slightly crisp. Cooking times may vary depending on your slow cooker, so check for doneness after 1 ½ hours.
Once the asparagus is cooked, transfer it to a serving platter. Drizzle any remaining juices from the slow cooker over the asparagus for added flavor.
If desired, squeeze fresh lemon juice over the asparagus or serve with lemon wedges on the side.