Heat butter over medium heat then add onion to the pan along with a pinch of salt and pepper. Saute onion until translucent then add in rice. Toast rice for about 60 seconds until you can begin to smell it.
Pour chicken broth into the pan along with another pinch salt and pepper. Stir once then bring to a boil. Place lid on pan then reduce heat to low. Cook for 15 minutes with lid on then stir in spinach to wilt right before serving. Check for seasoning and add more salt and pepper to taste. Stir in dill and garnish with minced scallions before serving,