Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Toss the cubed sweet potatoes with half of the avocado oil and a pinch of sea salt, then spread them in a single layer on the baking sheet.
Roast the sweet potatoes for 20-25 minutes until they are tender and caramelized on the edges.
While the potatoes roast, pat the salmon fillet dry with a paper towel and season with salt and pepper.
Heat the remaining avocado oil in a non-stick skillet over medium-high heat.
Place the salmon skin-side down in the pan and sear for 4-5 minutes until the skin is crisp, then flip and cook for another 2-3 minutes until desired doneness is reached.
Remove the salmon from the pan and let it rest; in the same pan, add the minced garlic and sauté for 30 seconds until fragrant.
Add the baby spinach to the pan and toss until just wilted, then remove from heat.
Plate the salmon alongside the roasted sweet potatoes and sautéed spinach, drizzling the lemon juice over the fish before serving.