Blend spice mixture in a small bowl and set aside.
Pat the fish and seafood dry using a dry paper towel. Generously season with 1/2 of the seasoning blend.
Heat 2-3 tbsp. oil in large skillet over medium-high heat. Once the skillet is hot, sear fish and seafood in batches, until golden brown on both top and bottom, but not cooked through, about 1-2 minutes per side. You can do this step in batches if you prefer or don't have enough room in the skillet. Once seared, remove from pan. Set all aside.
Reduce heat to medium, add about 2 tbsp. of the olive brine to the skillet and heat over medium heat to deglaze the pan, scraping up any pieces of remaining fish. Heat remaining oil in the same skillet and cook shallots with remaining spice blend until translucent and beginning to caramelize. Add 2 tbsp. olive brine one more time to deglaze the pan. Turn heat to medium-low, add olives and cover and simmer for 5 minutes. Add tomatoes and continue to cook until tomatoes begin to soften. Add in remaining brine, cover, and continue to simmer for 10-15 minutes.
Tuck seared fish and seafood, in between the cherry tomatoes and olives. Arrange the clams on top of everything. Cover pan and simmer until seafood is cooked to desired doneness and clam shells have opened, exposing the clams inside.