Score salmon skin , by making two slits on the skin side. Season with salt and black pepper. Stuff slits with some thyme leaves.
Heat Cast iron to medium high heat, and in oil and smashed garlic cloves (skin on).
Add salmon skin side down, push down with a spatula for about 30-45 seconds. Add in remaining thyme. Cook on the skin side for 4 minutes (Or about 2/3rds cooked, you will see a clear contrast on the side). Flip and cook for another 3-4 minutes. or until ready. (You can cook salmon on the sides too if you have a thicker cut )
For cucumber salad, combine all ingredients in a bowl and season to taste. Serve with salmon and fried plantains.