Preheat oven to 400 degrees. Place cast iron dutch oven on your stove top on medium-low heat.  Cut potatoes in half and place in a mixing bowl, add onions. Drizzle with olive oil and sprinkle with salt, pepper, and smoked paprika.  Use clean hands to toss together so everything is well coated.

Drop butter into your hot pan and immediately add potatoes and onions. Stir lightly to coat and then place lid on pan and place pan in pre-heated oven. Cook for 15 minutes  and then remove lid, stir potatoes, and return to oven for another 15-20 minutes until potatoes are soft and golden brown and onions are super soft and caramelized.  (You can stir occasionally if needed).