Combine carrots, butter, orange juice, honey, and 1 tsp. salt in a large wide heavy pot. Cover and cook over medium heat until carrots are crisp-tender, 10–12 minutes.
Meanwhile, rinse about 1 bunch worth of carrot tops and pat dry. Coarsely chop to yield about ⅔ cup. Combine tops with garlic, lemon zest, oil, and ¼ tsp. salt in a small bowl.
Uncover carrots and continue to cook, stirring occasionally, until sauce reduces enough to coat carrots, 8–10 minutes. Remove from heat. Stir in lemon juice and cayenne; adjust seasonings.
Transfer carrots to a platter and top with carrot top gremolata.
