1. Sprinkle tuna steaks on both sides with kosher salt; let stand 10 minutes at room temperature.
2. Meanwhile, heat 1 tablespoon oil in 12-inch skillet over medium-low heat. Add garlic and cook 4 to 5 minutes, turning occasionally, stirring until tender and lightly browned. Remove garlic with slotted spoon to cutting board; finely chop with parsley, cumin, and salt. Set aside.
3. Increase heat to medium-high; heat the oil in skillet until very hot. Add tuna and sear 30 seconds per side; transfer to a clean plate.
4. Add 1 tablespoon oil to skillet; reduce heat to medium. Add peppers and onions and cook 5 to 6 minutes, until just tender.
5. Reduce heat to medium-low; add garlic mixture, remaining 2 tablespoons oil, thyme, oregano, paprika, bay leaf, peppercorns, clam juice, and vinegar. Cover and simmer 10 to 12 minutes, until peppers are tender. Add tuna to skillet; cover and simmer 2 to 3 minutes. Remove from heat, spoon sauce over, cover and let stand 2 minutes more for medium-rare, 3 minutes for medium. Serve warm or at room temperature. Makes 4 servings.