Prep the oven: Preheat to 400°F (200°C).
Line a sheet pan with foil or parchment for easy cleanup.
Make the glaze base: In a small saucepan, combine apple cider, apple cider vinegar, maple syrup, Dijon, garlic, ginger, soy sauce, and red pepper flakes. Whisk to blend.
Reduce the glaze: Bring to a simmer over medium heat. Cook 8–12 minutes, stirring occasionally, until the liquid is reduced by about half and slightly syrupy.
You should see slow, glossy bubbles.
Finish the glaze: Remove from heat and whisk in the butter until melted and smooth. Taste and adjust with a pinch of salt or a splash more vinegar if you want more tang.
Season the salmon: Pat salmon dry with paper towels. Season both sides with salt and pepper.
Quick sear (optional but recommended): Heat olive oil in a large oven-safe skillet over medium-high.
Place salmon skin-side up and sear 1–2 minutes until lightly browned. Flip skin-side down.
Glaze and bake: Brush salmon generously with the apple cider glaze. Transfer the skillet to the oven (or move fillets to the prepared sheet pan).
Bake 6–9 minutes, depending on thickness, until the salmon flakes easily but is still moist in the center.
Broil for shine (optional): For extra caramelization, switch to broil for 1 minute at the end. Watch closely to avoid burning.
Rest and serve: Let the salmon rest 2 minutes. Spoon any pan juices over the top.
Garnish with thin apple slices and parsley if you like. Serve with rice, roasted sweet potatoes, or sautéed greens.