Heat a large ovenproof skillet over high heat. Add 1 tbsp oil to pan & swirl to coat.
Sprinkle filets with 1/2 tsp salt and 1/4 tsp pepper. Add filets, flesh side down, to pan and saute for 2 minutes. Place pan in oven cook at 400 for 3 minutes or until desire degree of doneness.
Heat a large cast-iron skillet over medium heat. Add remaining 2 btsp oil to pan & swirl to coat. Add garlic, and cook 2 minutes or until lightly browned, stirring occasionally. Increase heat to medium-high. Add tomatoes to pan, saute for 2 minutes or until skins blister, stirring frequently.
Remove pan from heat. Sprinkle tomato mixture with remaining salt & pepper, basil and shallots; toss to combine. Serve with fish.