1. Lay the fish fillets on a double layer of paper towel and pat both sides dry.
2. In a small bowl, mix together the cumin seeds, thyme, lemon zest, salt and pepper. With a spoon or your fingers, sprinkle the mixture to coat each side of the fillets to create a light crust. Press into the fish until it holds. Reserve any leftover bits.
3. Heat the olive oil in a large nonstick skillet over medium high heat until hot. Place the fillets skin side down. The skin will pucker and curl up. Use a flexible fish spatula or back end of a turner to flatten. The skin will relax in just a few seconds. Cook the fillets for 7-8 minutes until the bottom edges are brown. Use the spatula and flip the fillets. Let cook another 1-2 minutes until just cooked through, but not brown. Transfer to a plate and cover.
4. Bring the heat down to medium and let the pan cool for 1 minute. Add the garlic slices. Cook 1-2 minutes until they start to turn a light golden color. Scrape the bottom of the skillet with the spatula to release any of the brown bits. Toss in the romaine hearts and tomatoes along with any remaining bits of the cumin crust. Season with salt and pepper. Spoon the garlicky pan drippings over the romaine and tomatoes and cook 3-4 minutes until they are wilted and soft.
5. Place the fish fillets back in the pan. Spoon the drippings over the fish. Give a generous squeeze of fresh lemon juice. Season with salt and pepper and garnish with thyme sprigs. Serve immediately.