Lots of flexibility here - Substitute dried sage for your favorite dried herb mix. Instead of cod, you can use any fish you like, just adjust the cooking time based on thickness of the fillet.
Season the cod fillet on both sides with the salt, pepper and dried sage. Set aside.
Heat a saute pan over medium heat and add just 1 tablespoon of the butter. When the butter is bubbling and starting to get light brown, add the the chopped hazelnuts. Toast the hazelnuts in the butter, stirring constantly for 2 minutes. Remove the hazelnuts and let cool on paper towel. Keep the pan on the stove.
Add the remaining butter to the hot pan and add the cod. Cook for 2 minutes on one side, then flip the cod fillet. Turn the heat to medium-low. Add in the cherry tomatoes to the pan with the cod.
Cover loosely with a sheet of tin foil and let cook for an additional 2-4 minutes, gently shaking the pan every so often to turn the tomatoes. [fillet 1" thick = 2 minutes; fillet 2" thick = 4 minutes]
Serve the cod and tomatoes with chopped hazelnuts - make sure you drizzle a bit of the browned butter on each dish.