Heat a large non-stick pan over medium-high heat. When hot, add half of the butter. Add the onions and bell peppers. Cook, stirring often until the onions are soft and translucent, about 5-10 minutes. Add the garlic and cook until fragrant, 1 minute more. Remove the sautéed vegetables and do not clean the pan.

Add the remaining half of the butter as well as the mushrooms and asparagus. Cook until the mushrooms release their liquid and begin to brown and the asparagus is tender crisp, another 5-10 minutes. Transfer to the bowl with the other vegetables. Do not clean the pan.

Thoroughly dry the salmon and season both sides with salt and pepper. Sprinkle with half of the Old Bay seasoning. Heat the nonstick pan over medium heat, add a tiny bit of avocado oil and heat till shimmering. Add a salmon filet, skin side down and press it firmly against the pan for 15 seconds with a spatula. Repeat with each piece of salmon, pressing each one to ensure contact with the pan. Continue cooking fish, pressing occasionally to maintain skin contact with the pan until it is cooked to your liking, roughly 5 more minutes. Then flip the fish once and briefly cook on the other side for another 15 seconds or so. Transfer salmon to a plate, crispy skin side up (to prevent it from getting soggy) and do not clean the pan.

Add the spinach along with a couple teaspoons of water and wilt. Add back the vegetables along with the remaining half of the Old Bay seasoning, soy sauce, monk fruit, and hot sauce. Stir to combine evenly.

Divide the vegetables between two serving bowls and top with salmon, crispy skin side up. Serve with lemon wedges, if using.