Prepare the Onions: Thinly slice the onions and separate the slices. Place them in a bowl and toss lightly with the flour until evenly coated.
Cook the Onions: Heat the cooking oil in a large skillet over medium heat. Add the coated onions and cook, stirring occasionally, until golden brown and crispy, about 8–10 minutes.
Drain the Onions: Transfer the crispy onions to a paper towel-lined plate. Spread them out so excess oil can drain and the onions remain crisp.
Season the Sausages: In a small bowl, combine the paprika, garlic powder, onion powder, cayenne pepper, black pepper, and salt. Lightly coat the sausages with the seasoning mixture.
Cook the Sausages: Add the sausages to the same skillet over medium heat. Cook, turning occasionally, until browned on all sides and cooked through, about 12–15 minutes.
Add the Butter: Reduce the heat to low and add the butter. Allow it to melt around the sausages, gently turning them so they become coated in the flavorful butter and pan juices.
Add the Crispy Onions: Return some of the crispy onions to the skillet and gently toss them with the sausages. Reserve the remaining onions for topping.
Garnish and Serve: Transfer the sausages to a serving platter. Top generously with the remaining crispy onions and fresh parsley. Serve immediately.