Preheat your oven to 400°F (200°C).
Toss the cubed sweet potatoes with half of the avocado oil and a pinch of sea salt on a parchment-lined baking sheet.
Roast the sweet potatoes for 20-25 minutes, tossing halfway through, until they are tender and caramelized.
Pat the salmon fillet completely dry with a paper towel and season both sides with salt and black pepper.
Heat the remaining avocado oil in a cast-iron or non-stick skillet over medium-high heat.
Place the salmon in the pan skin-side down and sear for 4-5 minutes until the skin is crispy, then flip and cook for another 2-3 minutes until desired doneness.
Remove the salmon from the pan and set aside to rest.
In the same skillet, add the minced garlic and sauté for 30 seconds until fragrant.
Add the fresh spinach to the skillet and toss until just wilted, about 1-2 minutes.
Plate the salmon alongside the roasted sweet potatoes and sautéed spinach, drizzling the lemon juice over the fish and greens before serving.