Place garlic pieces in a cold, dry skillet. Add vegetable oil. Cook garlic on low heat until it starts to soften but does not get brown, about 8 to 10 minutes, stirring occasionally. When garlic is tender, remove skillet from heat; let garlic cool in the oil.
Place pumpkin seeds in a cold, dry skillet. Set heat to medium. Stir seeds until hot and fragrant but not browned, 3 to 5 minutes. Remove from heat. Transfer to a bowl.
Heat vegetable oil in a skillet over high heat. Add onion and Serrano pepper. Cool until edges start to brown and some bits begin to char, 3 to 5 minutes. Pour in apple juice. Reduce heat to medium and cook until liquid is reduced almost all the way and has a syrup-like consistency, about 5 minutes. Remove from heat.
Place pumpkin seeds, cilantro leaves, onion mixture, softened garlic and oil, lime juice, and salt in the bowl of a food processor. Cover and pulse on and off until mixture becomes a coarse paste, scraping down sides with a spatula a few times, 1 or 2 minutes. If mixture is quite thick, add a few tablespoons of apple juice or water (apple juice will make it sweeter).
Continue to process until mixture is to your desired consistency. Transfer to a bowl. Cover; refrigerate until chilled, about 2 hours. Taste, and adjust seasonings and acidity as needed with additional salt and/or apple cider vinegar.
