In a large bowl, combine grated zucchini, minced onion, melted butter and beaten egg, mix well (I like to use my hands for mixing). Stir in bread crumbs, Old Bay, salt and pepper, until well combined.
Using an ice cream scoop, shape mixture into 10 patties and flatten slightly with your hands.
In a shallow dish, gently dredge patties in flour.
In a large cast iron skillet, heat oil over medium-high heat until hot. Working in 2 batches, fry patties in oil until golden brown, about 3 to 4 minutes per side. Remove to a plate lined with paper towels. Serve hot with Greek yogurt or sour cream.