For the salmon: Pat the salmon dry. Place the salmon skin-side down on a piece of nonstick aluminum foil on a baking sheet or a cedar plank that was soaked in water for 1 to 2 hours. In a zigzag motion, drizzle the liquid smoke over the flesh of the salmon and brush it in; let rest 5 minutes. Season the salmon with salt.
For the rub: In a medium bowl, stir together the sugar, paprika, onion powder, garlic powder, chile flakes, salt and pepper. Gently pour the seasoning blend over the entire top of the salmon, patting it into the flesh evenly. Let rest at room temperature for 1 hour.
Preheat the oven or a grill to 300 degrees F.
Drizzle the olive oil over the salmon. Place the salmon on the foil directly onto the grill or in the oven (or the salmon on the plank). Cook until medium rare, 20 to 25 minutes, depending on the size.
For the easy salad: In a large bowl, toss the lettuce, onion and lemon juice. Sprinkle lightly with salt and a few grinds of black pepper. Rest for a few minutes, then drizzle over the olive oil and toss again.
Remove the salmon from the skin and flake over the salad.