Preheat oven to 450°F. Prepare 2 baking sheets with parchment paper and set aside. Prepare onions by slicing and separating into rings.
In a small bowl, whisk together flour, paprika, and 1/2 tsp of salt. In a wide, shallow bowl, whisk together buttermilk and eggs. Add half of the flour mixture to buttermilk mixture and whisk until smooth and thick.
In a separate bowl, combine panko breadcrumbs, olive oil and remaining salt.
Lightly dredge the onion rings in the flour mixture and drop in buttermilk batter. Drain excess and cover with bread crumb mixture. Arrange breaded onion rings on prepared baking sheets. Bake for 15-20 minutes, making sure to flip half way to ensure even crisping and browning.