Preheat oven to 400F and move the rack to the middle position. Line a large baking sheet with tin foil for easy clean-up. Add the salmon to the baking sheet skin-side down.
In a small saucepan, add the brown sugar, soy sauce, honey, water, garlic, and pepper. Whisk it together over medium-high heat until it just starts to simmer and the sugar dissolves (2-3 minutes).
Meanwhile, stir together the cornstarch and cold water until smooth. Add it to the saucepan and whisk until the mixture thickens (about 30 seconds or so). Immediately remove the teriyaki sauce from the heat so it doesn't burn.
Pour the mixture over the salmon and use a spoon or a brush to distribute it evenly. If the salmon is less than an inch thick in the thickest part, check the salmon after 12 minutes. If it's on the thicker side, bake it for 15-20 minutes or until it easily flakes with a fork.
Serve immediately with lemon wedges (the sauce is very sweet so I like to squeeze some lemon juice over top).