01 - Preheat the oven to 425°F. Line two large baking sheets with parchment paper or lightly coat them with nonstick spray.
02 - Separate onion slices into individual rings, discarding any very small inner rings or reserving them for another use.
03 - Arrange three shallow bowls: combine flour, paprika, garlic powder, salt, and black pepper in the first; whisk eggs and milk in the second; place panko breadcrumbs in the third.
04 - Dip each onion ring first in the flour mixture, shaking off excess, then in the egg wash, and finally coat thoroughly with panko breadcrumbs, pressing gently to adhere.
05 - Place the coated onion rings in a single layer on the prepared baking sheets. Drizzle or spray lightly with olive oil to enhance crispness.
06 - Bake for 20 to 25 minutes, flipping halfway through, until they are golden brown and crispy.
07 - While the rings bake, whisk together mayonnaise, sour cream, buttermilk, fresh herbs, seasonings, and lemon juice until the mixture is smooth. Chill until ready to serve.
08 - Serve the hot crispy onion rings alongside the chilled ranch dip.