Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Peel and dice the sweet potato into small half-inch cubes to ensure they roast quickly and evenly.
In a medium bowl, toss the sweet potato cubes with half of the olive oil, half of the sea salt, and all of the smoked paprika.
Spread the sweet potatoes on the baking sheet and roast for 15 minutes until they begin to brown at the edges.
Pat the cod fillet dry with a paper towel and season both sides with the remaining olive oil, sea salt, black pepper, and lemon juice.
Move the sweet potatoes to one side of the baking sheet and place the seasoned cod on the other side.
Return the sheet to the oven and bake for an additional 10 to 12 minutes until the cod is opaque and flakes easily with a fork.
While the fish and potatoes finish, place the fresh spinach in a small skillet over medium heat and sauté for 1 minute until just wilted.
In the same skillet, fry the egg to your preferred doneness, keeping the yolk runny to act as a natural sauce for the hash.
Plate the roasted sweet potatoes and wilted spinach, top with the baked cod fillet, and crown with the fried egg before serving.