Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper for easy cleanup.
Dice the red potatoes into small, even cubes and toss them with half of the olive oil and a pinch of the sea salt and black pepper.
Spread the potatoes on the baking sheet and roast for 15 minutes until they begin to soften and turn golden.
While potatoes roast, mince the garlic and finely chop the fresh dill and parsley.
Rub the salmon fillet with the remaining olive oil, minced garlic, chopped dill, and chopped parsley.
Move the potatoes to one side of the tray and place the seasoned salmon fillet on the other side.
Return the tray to the oven and roast for another 10-12 minutes until the salmon is flaky and cooked through.
In the final 2 minutes of roasting, place the fresh spinach in a pan over medium heat with the lemon juice and remaining salt and pepper, stirring until just wilted.
Plate the salmon and roasted potatoes over the bed of warm, wilted spinach and serve immediately.