Preparation Season fish with salt and pepper. Whisk lemon juice, vinegar, mustard, and 2 Tbsp. oil in a medium bowl. Add fish, toss to coat, and chill until ready to use. Cook polenta according to package directions. Meanwhile, heat remaining 1 Tbsp. oil in a large skillet over medium-high. Cook garlic, stirring occasionally, until beginning to brown, about 2 minutes. Transfer garlic to a plate. Cook bell pepper in same skillet, stirring frequently, until beginning to brown and soften, about 3 minutes. Add zucchini, cover, and cook 3 minutes. Reduce heat to medium-low. Add tomatoes, garlic, fish and dressing, 1 Tbsp. slivered basil, and 1 tsp. chopped oregano; season with salt and pepper. Cover and simmer just until fish is cooked through, about 5 minutes. Discard garlic, if desired. Divide polenta among bowls. Arrange fish mixture over. Garnish with basil and oregano.
Preparation Season fish with salt and pepper. Whisk lemon juice, vinegar, mustard, and 2 Tbsp. oil in a medium bowl. Add fish, toss to coat, and chill until ready to use. Cook polenta according to package directions. Meanwhile, heat remaining 1 Tbsp. oil in a large skillet over medium-high. Cook garlic, stirring occasionally, until beginning to brown, about 2 minutes. Transfer garlic to a plate. Cook bell pepper in same skillet, stirring frequently, until beginning to brown and soften, about 3 minutes. Add zucchini, cover, and cook 3 minutes. Reduce heat to medium-low. Add tomatoes, garlic, fish and dressing, 1 Tbsp. slivered basil, and 1 tsp. chopped oregano; season with salt and pepper. Cover and simmer just until fish is cooked through, about 5 minutes. Discard garlic, if desired. Divide polenta among bowls. Arrange fish mixture over. Garnish with basil and oregano.