Preheat the oven to 425°F/220°C. Choose a casserole dish large enough to hold the beans, tomatoes and fish.
Season the fish to taste with salt, pepper and smoky paprika
In a large bowl combine the diced tomatoes and beans. Stir in the olive oil, balsamic vinegar and other seasonings (to taste)
Transfer to the casserole dish and spread in an even layer. Scatter some thyme over top. Arrange the fish filets over the bean mixture and place lemon slices on top.
Cover the casserole with foil and cook until the fish is cooked properly (145°F/63°C internal temperature and flaky). Start checking after 12 to 15 minutes cooking time. The beans should be warmed through as well.
Depending on the type of fish and thickness of the filets, you may find it necessary to remove the fish and return the beans to the oven for 10 more minutes or so.