In medium bowl, combine salsa ingredients. Gently toss together to mix evenly. Set aside to marinate at room temperature for 30 minutes, or cover and refrigerate for up to 4 hours.
In large, resealable bag, combine 2 Tbsp olive oil, garlic, lemon juice, salt, and pepper. Add sablefish and turn to coat evenly. Refrigerate for 30 minutes or up to 2 hours.
In large nonstick frying pan, add remaining 1 Tbsp olive oil and butter over high heat. Tilt pan to spread evenly. Just as pan begins to smoke, add sablefish fillets in a single layer. Cook until seared on bottom, about 3 minutes, then flip fillets and sear the other side, about 3 more minutes. Reduce heat to medium and cook for a minute longer, depending on thickness of fillets. Cook until centers of fillets are just opaque and fish flakes easily.
Spoon Grape and Caper Salsa overtop and serve. Delicious served with shaved zucchini laced with chopped nuts, fresh basil, and mint.
Notes
Each serving contains: 515 calories; 20 g protein; 42 g total fat (9 g sat. fat, 0.2 g trans fat); 16 g total carbohydrates (12 g sugars, 2 g fiber); 397 mg sodium