Place salmon on a parchment-lined baking sheet skin-side down. Sprinkle with salt and pepper. Bake at 400 degrees for 25-40 minutes. NOTE: Frozen salmon will take longer, thawed salmon will take less time.
While the salmon is baking, prepare the sauce. Mix together all sauce ingredients in a small saucepan. Cook over medium-low heat until it begins to simmer. Simmer for 5-7 minutes. Remove from heat and let cool slightly.
Microwave sweet potatoes: For one sweet potato microwave for 5 minutes. For every additional sweet potato, add 2 minutes. (For 4 sweet potatoes microwave for 11 minutes.)
Remove sweet potatoes from microwave and mash. Top with butter and salt and pepper.
Wilt spinach. Heat avocado oil in a medium skillet. Add garlic and cook for 30 seconds. Add spinach one handful at a time until it is all wilted. Season with salt and pepper to taste.
To plate: Place salmon on a bed of wilted spinach and drizzle salmon with berry sauce. Place mashed sweet potatoes on the side.