How to Make It
In a small bowl, whisk the maple syrup with the lemon juice, both mustards and 1 tablespoon of the grapeseed oil.
Thread the salmon onto skewers and season all over with salt and pepper. In a large cast-iron skillet, heat 1 tablespoon of the oil until shimmering. Add half of the skewers and cook over moderate heat until browned on the bottom, 1 to 2 minutes. Flip the skewers and cook, basting with the mustard glaze and turning occasionally, until glazed and nearly cooked through, about 5 minutes total. Repeat with the remaining oil and skewers. Transfer to a platter and serve right away.