Peel and cube the sweet potato, then boil in a pot of water until fork-tender.
Drain the sweet potato and mash thoroughly until smooth, seasoning with a pinch of salt and pepper.
Pat the salmon fillet completely dry with paper towels and season the flesh side with salt.
Heat half of the olive oil in a 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 crisp.
Carefully flip the salmon and cook for an additional 2-3 minutes until the desired doneness is reached, then remove from the pan.
In the same skillet, add the remaining oil and the minced garlic, sautéing for 30 seconds until fragrant.
Add the fresh spinach to the skillet and toss until just wilted, about 1-2 minutes.
Plate the sweet potato mash, top with the garlic spinach and seared salmon, and finish with a squeeze of fresh lemon juice.