Place the salmon in a zip-top bag. Mix the soy sauce, orange juice, garlic, mustard, tomato paste, and lemon juice in a bowl. Pour into the bag with the salmon. Seal the bag, pressing out excess air. Marinate in the fridge for 4 to 6 hours.

Let fish return to room temperature. Place salmon (reserving marinade) on a pre-heated indoor or outdoor grill, skin side down. Cook for 5 to 8 minutes, depending on the thickness. Use a wide spatula to carefully flip to the other side and cook for another 4 to 5 minutes, or until it reaches your preferred level of doneness. (Note: Salmon should release easily from the grill; if it doesn’t, wait another 1 minute or 2 before flipping.) Keep in mind most salmon filets take just about 12 minutes to cook through, so pay close attention to avoid overcooking.

For extra flavor, lightly drizzle a few tablespoons of marinade on salmon during grilling. Discard leftover marinade.