How to Make It
Heat a large nonstick skillet over medium-high. Sprinkle fish with 1/4 teaspoon salt and 1/4 teaspoon pepper. Add 1 tablespoon oil to skillet; swirl to coat. Add fish; cook to desired degree of doneness, about 3 minutes on each side for medium. Remove fish from pan; discard drippings. (Do not wipe skillet clean.) Lightly tent fish with foil to keep warm.
Heat remaining 2 tablespoons oil in skillet over medium-high. Add garlic; cook, stirring often, until light golden brown, about 1 minute. Stir in thyme and tomatoes; cook, stirring often, until heated through, about 1 minute. Add stock and beans; bring to a simmer. Add spinach in batches, and cook, tossing gently, until spinach is wilted after each addition. Stir in lemon juice, olives, remaining 1/2 teaspoon salt, and remaining 1/4 teaspoon pepper. Divide bean mixture among 4 shallow bowls; nestle 1 fillet into each bowl.