Preheat your oven to 400°F (200°C) and line a small baking sheet with parchment paper.
Dice the Yukon Gold potatoes into half-inch cubes and toss them in a bowl with 1 teaspoon of olive oil, garlic powder, and half of the salt and pepper.
Spread the potatoes on the baking sheet and roast for 20-25 minutes, flipping halfway through, until they are golden brown and crispy.
Pat the salmon fillet completely dry with a paper towel and season both sides with the remaining salt and pepper.
Heat the remaining 1 teaspoon of olive oil in a non-stick skillet over medium-high heat until shimmering.
Place the salmon in the pan, skin-side down, and press gently with a spatula for 10 seconds to ensure even contact; cook for 4-5 minutes until the skin is very crispy.
Carefully flip the salmon and cook for another 2-3 minutes until it reaches your desired level of doneness, then remove it from the pan to rest.
In the same skillet, add the baby spinach and sauté for 1-2 minutes until just wilted.
Plate the roasted potatoes and sautéed spinach, top with the salmon fillet, and drizzle the entire dish with fresh lemon juice before serving.