TO MAKE THE TABBOULEH:
In a small pot, combine the lentils and water. Cover, raise the heat to high, and bring to a boil. Reduce the heat to low and simmer, covered, for 15 minutes, or until tender.
Meanwhile, in a bowl, toss together the oil, lemon juice, garlic, scallions, parsley, cucumber, tomatoes, and salt. When the lentils are cooked, drain, then add to the bowl and toss to combine. Taste and adjust the seasoning.
TO MAKE THE SALMON:
Rinse the salmon under cold water, then pat dry with a paper towel. Squeeze the lemon juice over the flesh side, then season with the salt.
Brush the salmon with 2 teaspoons of the oil. Heat a grill pan on medium high heat and add the remaining 1 teaspoon oil. When hot, cook the salmon, skin side down, for 4 minutes, or until the skin is crispy and releases easily from the pan. Flip and cook for 2 to 3 minutes, or until the fish is just cooked through. Spritz with any remaining lemon juice. Serve the salmon over the tabbouleh.