Step 1: Prepare the Cheesy Jalapeño Filling. In a medium bowl, combine the shredded cheddar cheese, softened cream cheese, chopped jalapeños, and garlic powder. Mix thoroughly until all ingredients are well combined and form a cohesive mixture.
Step 2: Prepare the Onion Rings for Filling. Carefully separate the onion rings. Take each individual onion ring and gently fill the cavity with a small amount of the cheesy jalapeño filling, pressing it lightly to secure.
Step 3: Set up the Breading Stations. In one shallow bowl, combine the all-purpose flour, 1 tsp salt, 1 tsp black pepper, and paprika. In another shallow bowl, pour the buttermilk. In a third shallow bowl, combine the panko breadcrumbs, 1 tsp salt, and 1 tsp black pepper.
Step 4: Coat the Onion Rings. Dip each filled onion ring first into the flour mixture, ensuring it's fully coated. Shake off any excess. Next, dip it into the buttermilk, letting any extra drip off. Finally, thoroughly coat the onion ring with the seasoned panko breadcrumbs, pressing gently to make sure the breadcrumbs adhere well.
Step 5: Fry the Onion Rings. Heat about 2-3 inches of vegetable oil in a deep fryer or large heavy-bottomed skillet to 375°F (190°C). Carefully place the coated onion rings into the hot oil in batches, being careful not to overcrowd the pan. Fry for 2-3 minutes per side, or until they are golden brown and crispy.
Step 6: Drain and Serve. Once fried, use a slotted spoon to remove the onion rings and place them on a wire rack set over paper towels to drain excess oil. Garnish with fresh cilantro and serve immediately with lime wedges and your favorite dipping sauce.