Preheat oven to 400°F (205℃).
Grease a 9x13 baking pan, oven-proof cast iron skillet, or baking sheet. If using a baking sheet, cover it with foil and then grease it for easier clean-up.
Season salmon fillets with pepper. Set aside.
In a medium mixing bowl, whisk together the garlic, ginger, soy sauce, brown sugar, sriracha, apple cider vinegar, water, and cornstarch.
Place salmon fillets into a large Tupperware bowl or resealable bag. Pour the marinade in and coat the fish well. Marinate for 20-30 minutes in the fridge.
After marinating, take the salmon fillets from the fridge and place them in a baking dish. Bake for 12-15 minutes or until flaky when poked with a fork. Cooking time varies depending on the thickness of salmon fillets.
While salmon is baking, pour the leftover marinade into a small saucepan. Heat on medium, bring to a boil, turn heat down, and simmer, stirring occasionally, until slightly thickened (3-4 minutes). Remove from heat and set aside.
Take salmon out of the oven when cooked to your liking. Serve on a plate, pour extra teriyaki sauce on top, or serve it on the side.
Garnish with green onions and serve with rice and broccoli.